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 A305629 #25 Jul 16 2018 04:53:00 %S A305629 0,0,1,1,1,1,1,1,2,2,2,2,0,3,3,1,3,5,2,2,4,2,1,4,3,2,4,1,4,4,2,4,4,3, %T A305629 1,3,2,4,12,3,2,7,1,7,15,3,4,6,3,8,8,2,4,10,6,7,7,3,6,16,3,4,6,3,8,7, %U A305629 4,5,11,5,4,7,5,8,12,2,12,8,4,16,9,3,8,24,6,8,11,5,8,19,3 %N A305629 Number of values of k, 0 < k < n, for which (2*n^2 + 2*k*n - k^2 - k)/2 is prime. %C A305629 It appears that a(A046174(n)) = 0. %o A305629 (PARI) a(n) = sum(k=1, n-1, isprime((2*n^2+2*k*n-k^2-k)/2)) %Y A305629 Cf. A046174. %K A305629 nonn %O A305629 0,9 %A A305629 _Gionata Neri_, Jul 08 2018