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 A036781 #18 Jul 08 2025 21:57:26
%S A036781 1,3,6,13,38,159,880,5921,46242,409123,4037924,43954725,522956326,
%T A036781 6749977127,93928268328,1401602636329,22324392524330,378011820620331,
%U A036781 6780385526348332,128425485935180333,2561327494111820334,53652269665821260335,1177652997443428940336
%N A036781 a(n) = n + Sum_{k=0..n} k!.
%H A036781 Alois P. Heinz, <a href="/A036781/b036781.txt">Table of n, a(n) for n = 0..400</a>
%p A036781 a:= proc(n) option remember; `if`(n=0, 1, a(n-1)+1+n!) end:
%p A036781 seq(a(n), n=0..30); # _Alois P. Heinz_, Jan 05 2015
%t A036781 Module[{nn=30,f},f=Accumulate[Range[0,nn]!];Table[n+f[[n]],{n,nn}]]-1 (* _Harvey P. Dale_, Nov 04 2020 *)
%t A036781 Module[{nn=30,f},f=Accumulate[Range[0,nn]!];Total/@Thread[{f,Range[0,nn]}]] (* _Harvey P. Dale_, Jan 31 2023 *)
%Y A036781 A003422[ n ] + n.
%Y A036781 Cf. A007489.
%K A036781 nonn
%O A036781 0,2
%A A036781 _N. J. A. Sloane_