OFFSET
1,1
LINKS
Math Stackexchange, Marko Riedel et al., N digit numbers with no digit appearing exactly twice.
FORMULA
E.g.f.: Sum_{q=1..N} C(10,q)*(exp(z)-z^2/2-1)^q.
E.g.f.: (exp(z)-z^2/2)^10.
EXAMPLE
Computing the value for n=1 the ten one-digit numbers 0-9 all qualify.
Computing the value for n=2 of two-digit numbers 00-99 all qualify except those consisting of a double digit (00, 11, ..., 99).
MAPLE
STNE2 := (n, k)->n!*coeftayl((exp(z)-z^2/2-1)^k/k!, z=0, n);
a(N) := N -> add(combinat:-binomial(10, q)*STNE2(N, q)*q!, q = 1 .. N)
MATHEMATICA
With[{nn=20}, Rest[CoefficientList[Series[(Exp[x]-x^2/2)^10, {x, 0, nn}], x] Range[0, nn]!]] (* Harvey P. Dale, Oct 07 2024 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Marko Riedel, Apr 30 2016
STATUS
approved