login
A294008
Number of multisets of exactly six nonempty words with a total of n letters over n-ary alphabet such that within each prefix of a word every letter of the alphabet is at least as frequent as the subsequent alphabet letter.
2
1, 2, 7, 22, 73, 240, 818, 2816, 9967, 36080, 133875, 509676, 1990984, 7990628, 32936173, 139548808, 607402437, 2716780286, 12476624346, 58818236078, 284350933608, 1408898449946, 7146679566822, 37085526689402, 196654885016221, 1064783059174600
OFFSET
6,2
LINKS
FORMULA
a(n) = [x^n y^6] Product_{j>=1} 1/(1-y*x^j)^A000085(j).
MAPLE
g:= proc(n) option remember; `if`(n<2, 1, g(n-1)+(n-1)*g(n-2)) end:
b:= proc(n, i) option remember; series(`if`(n=0 or i=1, x^n,
add(binomial(g(i)+j-1, j)*b(n-i*j, i-1)*x^j, j=0..n/i)), x, 7)
end:
a:= n-> coeff(b(n$2), x, 6):
seq(a(n), n=6..35);
CROSSREFS
Column k=6 of A293808.
Cf. A000085.
Sequence in context: A294006 A322573 A294007 * A294009 A294010 A294011
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Oct 21 2017
STATUS
approved