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
Robert Israel, Table of n, a(n) for n = 0..10000
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
KEYWORD
base,easy,nonn
AUTHOR
Carl R. White, Jan 16 2008
STATUS
approved