OFFSET
0,3
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..200
FORMULA
E.g.f.: Sum_{n>=0} exp(x*n*(n+1)/2).
a(n) ~ exp(3) * n^(2*n) / ((exp(2)-1) * 2^n).
MATHEMATICA
Table[n!*SeriesCoefficient[Sum[Exp[x*k*(k+1)/2], {k, 0, n}], {x, 0, n}], {n, 0, 20}]
Flatten[{1, Table[Sum[(k*(k+1)/2)^n, {k, 1, n}], {n, 1, 20}]}]
PROG
(PARI) a(n) = sum(k=0, n, (k*(k+1)/2)^n); \\ Michel Marcus, Aug 24 2023
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vaclav Kotesovec, Nov 01 2014
EXTENSIONS
New name from Peter Bala, Aug 18 2023
STATUS
approved