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A136701 Final nonzero digit of n! in base 15. 15
1, 1, 2, 6, 9, 8, 3, 6, 3, 12, 3, 3, 6, 3, 12, 12, 12, 9, 12, 3, 9, 9, 3, 9, 6, 9, 9, 3, 9, 6, 12, 12, 9, 12, 3, 12, 12, 9, 12, 3, 3, 3, 6, 3, 12, 6, 6, 12, 6, 9, 12, 12, 9, 12, 3, 6, 6, 12, 6, 9, 6, 6, 12, 6, 9, 9, 9, 3, 9, 6, 3, 3, 6, 3, 12, 9, 9, 3, 9, 6, 12, 12, 9, 12, 3, 12, 12, 9, 12, 3, 3, 3, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
From Robert Israel, Jun 08 2018: (Start)
For n >= 6, a(n) is 3, 6, 9 or 12.
For k >= 2, a(5*k) = a(5*k+1) = a(5*k+3). (End)
LINKS
EXAMPLE
6! = 720 decimal = 330 quindecimal, so a(6) = 3.
MAPLE
a:= 1: b:= 0: R[0]:= 1:
for n from 1 to 100 do
alpha:= padic:-ordp(n, 3);
beta:= padic:-ordp(n, 5);
a:= a * n/3^alpha/5^beta;
b:= b + alpha - beta;
R[n]:= a * 3 &^ b mod 15;
od:
seq(R[n], n=0..100); # Robert Israel, Jun 08 2018
MATHEMATICA
nzd[x_]:=If[x[[-1, 1]]==0, x[[-2, 1]], x[[-1, 1]]]; Table[nzd[Split[IntegerDigits[n!, 15]]], {n, 0, 100}] (* Harvey P. Dale, Jul 11 2023 *)
CROSSREFS
Sequence in context: A242433 A011046 A246828 * A175030 A335027 A263178
KEYWORD
base,easy,nonn
AUTHOR
Carl R. White, Jan 16 2008
STATUS
approved

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Last modified June 21 01:13 EDT 2024. Contains 373535 sequences. (Running on oeis4.)