Yes, it is less valid. For instance, consider the sequence 41, 43, 47, 53, 61, ... Looks like a sequence of primes doesn't it. And notice how the difference keeps increasing by 2 each time. Heck, I'll add some more, 41, 43, 47, 53, 61, 71, 83, 97, 113, .... More primes! OMG, it's a sequence of primes! I'll add some more, 41, 43, 47, 53, 61, 71, 83, 97, 113, 131, 151, 173, more primes! Am I working with some kind of prime generating sequence? Can I find infinitely many primes using this "Increase the difference by 2 each time" rules? I've got a dozen primes so far, infact, I can give
consecutive primes.
But when I use algebra to work out that the formula is f(n) = n^2 + n + 41 I immediately see it cannot generate primes indefinitely because n=40 and n=41 are trivially not prime. A sequence of more than 3 dozen samples falls apart. And you, Raphie, only look at 6~12 terms in any of the sequences you talk about.
In a general sense, you make a good point, Alphanumeric, but let me note that if one were predicting that all numbers in the x^2 + x + 41 series would be prime, this is eminently verifiable and falsifiable. In other words, a prediction is being made that can then be tested:
"Conjecture:"
x^2 + x + 41 = y | y is prime for all x
For values up to 39, all the numbers are prime, but now:
Let x = 40; y = 1681 = 41 * 41 (Conjecture is FALSE)
Let x = 41; y = 1763 = 41 * 43 (Conjecture is FALSE)
In many ways, this is a no-brainer, since for x = 40, you have a formula that reduces to n^2 + (2n+1), the formula for (n+1)^2, and for x = 41, you've a formula that reduces to n^2 + 2n, the formula for (n+1)^2 - 1, equal in all cases to (n)*(n+2)
In any case, funny you should post that particular formula as a basis by which to support claims of "lack of validity" since it is a quite famous formula in mathematical history. I will actually take the time to type out verbatim almost a full page from "The Music of the Primes" by Marcus du Sautoy (p. 45) as it a ) has bearing on your post, and b ) I believe will be informative for others:
[Note: Ah the wonders of the information age. I didn't have to type this all in as the full text can be found here:
http://d.scribd.com/docs/174tfruz3w4l96sh0eej.pdf===========================================================
Above all else, Euler loved calculating prime numbers. He produced tables of all the
primes up to 100,000 and a few beyond. In 1732, he was also the first to show that
Fermat's formula for primes, 2^2^n + 1, broke down when N = 5. Using new theoretical ideas,
he managed to show how to crack this ten-digit number into a product of two smaller
numbers. One of his most curious discoveries was a formula that seemed to generate an
uncanny number of primes. In 1772, he calculated all the answers that you get when you
feed the numbers from 0 to 39 into the formula x^2 + x + 41. He got the following list:
41, 43, 47, 53, 61, 71, 83, 97, 113, 131, 151, 173, 197, 223, 251, 281, 313, 347, 383, 421,
461, 503, 547, 593, 641, 691, 743, 797, 853, 911, 971, 1,033, 1,097, 1,163, 1,231, 1,301,
1,373, 1,447, 1,523, 1,601
It seemed bizarre to Euler that you could generate so many primes with this formula. He
realised that the process would have to break down at some point. It might already be
clear to you that when you input 41, the output has to be divisible by 41. Also, for x = 40
you get a number which is not prime.
Nonetheless, Euler was quite struck by his formula's ability to produce so many primes. He
began to wonder what other numbers might work instead of 41. He discovered that in
addition to 41 you could also choose q = 2, 3, 5, 11, 17, and the formula x^2 + x + q would
spit out primes when fed numbers from 0 to q — 2.
But finding such a simple formula for generating all the primes was beyond even the great
Euler. As he wrote in 1751, 'There are some mysteries that the human mind will never
penetrate. To convince ourselves we have only to cast a glance at tables of primes and we
should perceive that there reigns neither order nor rule.' It seems paradoxical that the
fundamental objects on which we build our order-filled world of mathematics should
behave so wildly and unpredictably.
It would turn out that Euler had been sitting on an equation that would break the prime number deadlock. But it would take another hundred years, and another great mind, to show what Euler could not.
That mind belonged to Bernhard Riemann.
===========================================================
Now let me add the following:
If one could manage somehow to generate a similarly elegant and simple formula for Kissing Numbers as Euler did for primes (as you know I believe Kissing Numbers are related to the primes...), one would quadruple in one fell swoop the number of known kissing numbers, from 10 to 40. One might also be setting the stage for the next Riemann to come along 100 hundred years from now.
Just a thought.
Best,
Raphie