A136699 Final nonzero digit of n! in base 13.

1, 1, 2, 6, 11, 3, 5, 9, 7, 11, 6, 1, 12, 12, 12, 11, 7, 2, 10, 8, 4, 6, 2, 7, 12, 1, 2, 2, 4, 12, 9, 6, 10, 5, 1, 9, 12, 2, 11, 7, 7, 1, 3, 12, 8, 9, 11, 10, 12, 3, 7, 6, 11, 11, 9, 1, 4, 7, 3, 8, 12, 4, 1, 11, 2, 10, 10, 7, 8, 6, 4, 11, 12, 5, 6, 8, 10, 3, 5, 5, 10, 4, 3, 2, 12, 6, 9, 3, 4, 5, 8, 4

Offset

0,3

Links

Table of n, a(n) for n=0..91.

Example

6! = 720 decimal = 435 tridecimal, so a(6) = 5.

Mathematica

f[s_List] := Block[{a = s[[ -1]], len = Length@s}, Append[s, If[Mod[len, 13] == 0, Mod[a*len/13, 13], Mod[a*len, 13]]]]; Nest[f, {1}, 100] (* Robert G. Wilson v, May 03 2009 *)
f[n_] := Block[{id = IntegerDigits[n!, 13]}, While[id[[ -1]] == 0, id = Most@id]; id[[ -1]]]; Table[ f@n, {n, 0, 100}] (* Robert G. Wilson v, May 03 2009 *)

Crossrefs

Cf. A000142, A136690, A136691, A136692, A136693, A136694, A136695, A136696, A008904, A136697, A136698, A136700, A136701, A136702.

Sequence in context: A162582 A123098 A351716 * A033710 A243157 A274689

Adjacent sequences: A136696 A136697 A136698 * A136700 A136701 A136702

Keyword

base,easy,nonn

Author

Carl R. White, Jan 16 2008

Status

approved