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 A099556 #10 Nov 21 2024 09:52:21
%S A099556 1,2,5,18,91,604,5123,53808,679389,10107934,174544505,3451802006,
%T A099556 77302457079,1942469215432,54339334903015,1680597906265988,
%U A099556 57116435383949097,2121725700531106842,85740960774906267853,3753239245360442525498,177284859933198522968819,9004760569281510790598100
%N A099556 a(n) = Sum_{k=0..2*n} (n - floor(k/2))^k.
%F A099556 Row sums of triangle A099555.
%o A099556 (PARI) a(n)=sum(k=0,2*n,(n-k\2)^k)
%Y A099556 Cf. A099555.
%K A099556 nonn,easy
%O A099556 1,2
%A A099556 _Paul D. Hanna_, Oct 22 2004
%E A099556 a(13) and following terms from _Georg Fischer_, Nov 21 2024