

A111177


Number of base n numbers in which each digit appears at most once (all unnecessary 0's deleted).


0



4, 21, 130, 913, 7176, 62629, 602806, 6356865, 72994348, 907497301, 12152572554, 174476220241, 2674434002800, 43603430324133, 753581024080126, 13763517571878529, 264919276238885076, 5360264479811601685
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OFFSET

2,1


COMMENTS

Finite expansions after the "decimal" point are allowed, but there must be a number before it (so we can have 0.1, but not .01).


LINKS



FORMULA

a(n)=Sum(i=0, n1) (i^2+i+1)(n1)!/(n1i)!; n>1


EXAMPLE

a(2)=4 because in the binary system only the numbers 0; 1; 0.1; 10 can be written with each digit used at most once (all unnecessary 0's deleted).


MATHEMATICA

f[n_] := Sum[(i^2 + i + 1)(n  1)!/(n  1  i)!, {i, 0, n  1}]; Table[ f[n], {n, 2, 19}] (* Robert G. Wilson v *)


CROSSREFS



KEYWORD

nonn,base


AUTHOR

Rafael Hofman (mathematics287(AT)yahoo.de), Oct 22 2005


EXTENSIONS



STATUS

approved



