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

Author

Carl R. White, Jan 16 2008

Keywords

• base
• easy
• nonn

Examples

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

Crossrefs

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

Programs

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 *)