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 A349928 #13 Dec 06 2021 03:59:05
%S A349928 1,3,20,246,4481,107129,3157836,110504876,4473749677,205615442135,
%T A349928 10574135574388,601527803412298,37500537926181449,2542321872054610333,
%U A349928 186209553386691383388,14653121207168215024624,1232879877057607865696085,110444572988776439826640683
%N A349928 a(n) = Sum_{k=0..n} (k+n)^k.
%F A349928 a(n) ~ 2^n * n^n. - _Vaclav Kotesovec_, Dec 06 2021
%t A349928 a[0] = 1; a[n_] := Sum[(k + n)^k, {k, 0, n}]; Array[a, 18, 0] (* _Amiram Eldar_, Dec 05 2021 *)
%o A349928 (PARI) a(n) = sum(k=0, n, (k+n)^k);
%Y A349928 Cf. A026898, A031973, A050409, A060946, A062970, A074209, A116149, A117887.
%K A349928 nonn
%O A349928 0,2
%A A349928 _Seiichi Manyama_, Dec 05 2021