OFFSET
0,2
COMMENTS
species is SEQ_10(SET_(!=3)(Z))
LINKS
Math Stackexchange, Marko Riedel et al., N digit numbers with no digit appearing exactly twice.
FORMULA
E.g.f.: (exp(z)-z^3/3!)^10.
EXAMPLE
a(3) = 10^3-10 because all 3-letter strings qualify except the strings containing only one type of letter.
MAPLE
a := n->n!*coeftayl((exp(z)-z^3/3!)^10, z=0, n);
MATHEMATICA
With[{nn=20}, CoefficientList[Series[(Exp[x]-x^3/3!)^10, {x, 0, nn}], x] Range[ 0, nn]!] (* Harvey P. Dale, Apr 08 2019 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Marko Riedel, May 01 2016
STATUS
approved