This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A226567 #35 Aug 21 2025 15:22:22 %S A226567 7,10,13,16,17,19,22,25,27,28,31,32,34,37,38,42,43,45,46,47,49,52,55, %T A226567 57,58,59,61,62,64,66,67,70,71,72,73,76,77,79,80,82,85,87,88,91,92,93, %U A226567 94,97,100,101,102,103,104,106,107,108,109,110,115,117,118,121 %N A226567 Numbers k such that 2*k+1 is neither a square nor a prime. %C A226567 The natural numbers A000027 that are not in A005097 and A046092. %C A226567 A226567 = Complement(A000027, A005097, A046092). - _Zak Seidov_, Jul 08 2013 %H A226567 Robert Israel, <a href="/A226567/b226567.txt">Table of n, a(n) for n = 1..10000</a> %e A226567 a(2)=10 is a term because 2*10+1 = 21 is neither a square nor a prime. %p A226567 remove(n -> issqr(2*n+1) or isprime(2*n+1), [$1..1000]); # _Robert Israel_, Jun 16 2017 %t A226567 Select[Range[200], ! PrimeQ[2 # + 1] && ! IntegerQ[Sqrt[2 # + 1]] &] (* _T. D. Noe_, Jun 13 2013 *) %Y A226567 Cf. A000027, A005097, A046092. %K A226567 nonn,changed %O A226567 1,1 %A A226567 _César Aguilera_, Jun 13 2013