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 A023591 #12 Sep 09 2024 02:40:46 %S A023591 1,1,1,1,1,3,1,1,1,1,2,2,1,1,1,1,1,1,3,1,2,1,1,1,1,1,2,1,1,1,1,1,2,2, %T A023591 1,1,2,1,1,1,1,2,1,2,1,1,2,1,1,3,1,1,1,1,1,1,2,1,1,1,4,1,1,1,1,1,1,3, %U A023591 1,1,1,1,2,2,1,1,1,1,1,2,1,1,1,2,1,1,1,1,1,2,1,1,2,1,3,1,1,1,1 %N A023591 Greatest exponent in prime-power factorization of 2*prime(n)+1. %F A023591 a(n) = A051903(A072055(n)). - _Amiram Eldar_, Sep 09 2024 %p A023591 A023591 := proc(n) %p A023591 A051903(2*ithprime(n)+1) ; %p A023591 end proc: # _R. J. Mathar_, Jul 08 2015 %t A023591 a[n_] := Max[FactorInteger[2*Prime[n] + 1][[;;, 2]]]; Array[a, 100] (* _Amiram Eldar_, Sep 09 2024 *) %o A023591 (PARI) a(n) = vecmax(factor(2*prime(n)+1)[,2]); \\ _Michel Marcus_, Apr 20 2021 %Y A023591 Cf. A051903, A072055. %K A023591 nonn %O A023591 1,6 %A A023591 _Clark Kimberling_