A246447 - OEIS

%I #26 Oct 02 2014 23:11:29

%S 10,15,26,35,50,63,80,99,122,143,170,195,224,255,290,323,362,399,440,

%T 483,530,575,624,675,728,783,842,899,962,1023,1088,1155,1224,1295,

%U 1370,1443,1520,1599,1682,1763,1850,1935,2024,2115,2210,2303,2400,2499,2600

%N The odd primes squared plus 1 and the composites squared minus 1.

%C The odd primes squared plus 1 and the nonprimes squared minus 1 are the numerators or denominators of an infinite product converging to 1 whose denominators or numerators, conversely, are the squares of said numbers, that is, (p^2+1/p^2)*(q^2-1)/q^2)..., where p is an odd prime and q is a nonprime.

%C Union of A066872 and (A062312 - 1) with 0 and 5 removed. - _Robert Israel_, Aug 26 2014

%H Jens Kruse Andersen, <a href="/A246447/b246447.txt">Table of n, a(n) for n = 1..10000</a>

%o (PARI) lista(nn) = {for (n=3, nn, if (isprime(n), print1(n^2+1, ", "), print1(n^2-1, ", ")););} \\ _Michel Marcus_, Aug 26 2014

%o (Python)

%o for n in range(3,10**3):

%o ..if isprime(n):

%o ....print(n**2+1,end=', ')

%o ..else:

%o ....print(n**2-1,end=', ') # _Derek Orr_, Sep 19 2014

%Y Cf. A066872, A062312.

%K nonn,easy

%O 1,1

%A _Leo Depuydt_, Aug 26 2014

%E More terms from _Michel Marcus_, Aug 26 2014