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 A236263 #23 Jan 22 2014 03:59:15 %S A236263 0,0,0,0,0,1,1,0,1,1,1,1,1,2,1,0,0,1,2,3,3,4,5,4,4,5,7,4,5,6,6,5,5,5, %T A236263 7,6,7,9,7,8,7,7,5,11,8,8,8,11,8,7,5,10,6,9,8,10,7,8,10,9,7,8,9,13,8, %U A236263 8,9,10,6,11,10,7,7,9,11,13,8,11,13,11,14,6 %N A236263 a(n) = |{0 < k < n: m = phi(k)/2 + phi(n-k)/8 is an integer with m! + prime(m) prime}|, where phi(.) is Euler's totient function. %C A236263 It seems that a(n) > 0 for all n > 17. (We have verified this for n up to 13000.) If a(n) > 0 infinitely often, then there are infinitely many positive integers m with m! + prime(m) prime. %C A236263 See also A236265 for a similar sequence. %H A236263 Zhi-Wei Sun, <a href="/A236263/b236263.txt">Table of n, a(n) for n = 1..8100</a> %e A236263 a(18) = 1 since phi(3)/2 + phi(15)/8 = 1 + 1 = 2 with 2! + prime(2) = 2 + 3 = 5 prime. %e A236263 a(356) = 1 since phi(203)/2 + phi(153)/8 = 84 + 12 = 96 with 96! + prime(96) = 96! + 503 prime. %e A236263 a(457) = 1 since phi(7)/2 + phi(450)/8 = 3 + 15 = 18 with 18! + prime(18) = 18! + 61 = 6402373705728061 prime. %t A236263 q[n_]:=IntegerQ[n]&&PrimeQ[n!+Prime[n]] %t A236263 f[n_,k_]:=EulerPhi[k]/2+EulerPhi[n-k]/8 %t A236263 a[n_]:=Sum[If[q[f[n,k]],1,0],{k,1,n-1}] %t A236263 Table[a[n],{n,1,100}] %Y A236263 Cf. A000010, A000040, A000142, A063499, A064278, A064401, A236241, A236256, A236265. %K A236263 nonn %O A236263 1,14 %A A236263 _Zhi-Wei Sun_, Jan 21 2014