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 A216045 #12 Feb 14 2021 15:19:45
%S A216045 1,6,30,145,151,592,732,3895,87806,292432
%N A216045 Numbers k such that Sum_{j=1..k-1} (4j)!/5^j is an integer.
%C A216045 Next term is > 1500000.
%t A216045 seq={}; sum=0; fak=1; k=0; While[k<10000, sum+=fak; If[Denominator[sum]==1, AppendTo[seq,k+1]]; k++; fak*=4*k*(4*k-1)*(4*k-2)*(4*k-3)/5;]; seq
%Y A216045 Cf. A215972, A216042, A216043, A216044.
%K A216045 nonn,more
%O A216045 1,2
%A A216045 _Vaclav Kotesovec_, Aug 30 2012