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 A089043 #7 Oct 02 2016 17:49:46 %S A089043 0,5,35,577,14399,518401,25401599,1625702401,131681894399, %T A089043 13168189440001,1593350922239999,229442532802560001, %U A089043 38775788043632639999,7600054456551997440001,1710012252724199423999999,437763136697395052544000001,126513546505547170185215999999 %N A089043 a(n) = n!^2 + (-1)^n. %C A089043 p = 2*n+1 is prime iff it divides a(n) (Wilson's theorem) for instance let n=5, p =11 : a(5) = 14399 = 11*1309, so 11 is prime. %F A089043 a(n) = n^2*(a(n-1)-(-1)^(n-1))+(-1)^n. %e A089043 a(5) = 14399 because 14399=(5!)^2+(-1)^5. %o A089043 (PARI) a(n) = n!^2+(-1)^n; \\ _Michel Marcus_, Oct 02 2016 %K A089043 easy,nonn %O A089043 1,2 %A A089043 Serge Boisse (serge.boisse(AT)aviation-civile.gouv.fr), Dec 02 2003 %E A089043 Offset corrected and edited by _Michel Marcus_, Oct 02 2016