OFFSET
2,5
COMMENTS
Terms computed by Michael Trott.
LINKS
Eric Weisstein's World of Mathematics, Steffi Problem
EXAMPLE
In base 2, there are no solutions for 1, so a(2)=0. In base 3, there are no solutions for 12, so a(3)=0. In base 4, there is a single solutions for 123, so a(4)=1. In base 5, there is a single solution with the digits 1234: 4312_5/1234_5 = 3, so a(5)=1.
MATHEMATICA
f[n_] := Block[{p = FromDigits[ #, n] & /@ Permutations[ Range[n - 1]]}, Sum[ Length[ Select[ p/p[[i]], IntegerQ[ # ] &]], {i, (n - 1)!}] - (n - 1)! ]; Table[ f[n], {n, 2, 9}] (* Robert G. Wilson v, Jul 15 2005 *)
CROSSREFS
KEYWORD
nonn,hard,base,more
AUTHOR
Eric W. Weisstein, Feb 05 2003
EXTENSIONS
Prepended a(2)=0, added a(13) - Giovanni Resta, Feb 24 2013
STATUS
approved