A349928 a(n) = Sum_{k=0..n} (k+n)^k.

1, 3, 20, 246, 4481, 107129, 3157836, 110504876, 4473749677, 205615442135, 10574135574388, 601527803412298, 37500537926181449, 2542321872054610333, 186209553386691383388, 14653121207168215024624, 1232879877057607865696085, 110444572988776439826640683

Offset: 0

Author

Seiichi Manyama, Dec 05 2021

Keywords

• nonn

Crossrefs

Cf. A026898, A031973, A050409, A060946, A062970, A074209, A116149, A117887.

Programs

Mathematica

a[0] = 1; a[n_] := Sum[(k + n)^k, {k, 0, n}]; Array[a, 18, 0] (* Amiram Eldar, Dec 05 2021 *)

PARI

a(n) = sum(k=0, n, (k+n)^k);

Formula

a(n) ~ 2^n * n^n. - Vaclav Kotesovec, Dec 06 2021