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 A107875 #5 Feb 27 2013 18:19:54
%S A107875 1,5,28,220,2380,33649,593775,12620256,314457495,8996462475,
%T A107875 290752384208,10477677064400,416579843773639,18114175790089400,
%U A107875 855130180330364620,43553532185070076800,2380434572658017204175
%N A107875 Column 1 of triangle A107873; a(n) = C( n*(n+1)/2 + n+3, n).
%t A107875 Table[Binomial[(n(n+1))/2+n+3,n],{n,0,20}] (* _Harvey P. Dale_, Feb 27 2013 *)
%o A107875 (PARI) a(n)=binomial(n*(n+1)/2+n+3,n)
%Y A107875 Cf. A107873, A107874.
%K A107875 nonn
%O A107875 0,2
%A A107875 _Paul D. Hanna_, Jun 04 2005