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 A217551 #16 Oct 12 2012 13:51:31 %S A217551 1,828,508,239499435,4693095288000,561589459200,148245349824000 %N A217551 Smallest numbers n, for a given s, such that s! + n^2 and (s+3)! + n^2 are squares. %C A217551 The corresponding values of s are: 4, 8, 9, 15, 21, 24, 27. %e A217551 4! + 1 = 5^2 and 7! + 1 = 71^2. %e A217551 8! + 828^2 = 852^2 and 11! + 828^2 = 6372^2. %o A217551 (PARI) for(n=4,30,a=n!;b=((n+3)*(n+2)*(n+1)-1)*a;c=divisors(b);for(i=2,#c-1,s=c[i];r=b\s;if(r<s,next(2),d=abs(s-r)/2;t=d^2-a;if(issquare(t),print([n,d,sqrtint(t)]))))) %Y A217551 Cf. A217277, A217541, A217550, A217551, A217553. %K A217551 nonn %O A217551 1,2 %A A217551 _Robin Garcia_, Oct 06 2012