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 A120387 #7 May 29 2015 06:31:33
%S A120387 0,1,2,6,9,15,20,0,0,45,54,66,77,0,0,120,135,153,170,0,0,231,252,0,0,
%T A120387 0,0,378,405,435,464,0,0,0,0,630,665,0,0,780,819,861,902,0,0,1035,
%U A120387 1080,0,0,0,0,1326,1377,0,0,0,0,1653,1710,1770,1829,0,0,0,0,2145,2210,0,0,2415
%N A120387 c(n) mod b(n) where c(n) = (n-1)! and b(n) = Sum_{i=1..n} i.
%F A120387 For n>1: if neither n nor n+1 is prime, then a(n)=0. Otherwise, a(n)=n(n-1)/2 - 1 for odd n and a(n)=n(n-1)/2 for even n. - _Ivan Neretin_, May 29 2015
%e A120387 a(5) = (5-1)! mod (1+2+3+4+5) = 24 mod 15 = 9.
%p A120387 P:=proc(n) local i,k; for i from 1 by 1 to n do print((i-1)! mod sum('k','k'=0..i)); od; end: P(100);
%Y A120387 Cf. A000217, A116536.
%Y A120387 Cf. A226718, A119690.
%K A120387 easy,nonn
%O A120387 1,3
%A A120387 _Paolo P. Lava_, Jun 30 2006