OFFSET
0,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..481
FORMULA
E.g.f.: exp(Sum_{j=1..3} (exp(j*x)-1)/j).
EXAMPLE
a(2) = 15: 11, 12, 13, 14, 21, 22, 23, 24, 25, 31, 32, 33, 34, 35, 36.
MAPLE
b:= proc(n, m) option remember; `if`(n=0, 1,
add(b(n-1, max(m, j)), j=1..m+3))
end:
a:= n-> b(n, 0):
seq(a(n), n=0..25);
# second Maple program:
a:= n-> n!*coeff(series(exp(add((exp(j*x)-1)/j, j=1..3)), x, n+1), x, n):
seq(a(n), n=0..25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jun 17 2018
STATUS
approved