A136695 Final nonzero digit of n! in base 8.

1, 1, 2, 6, 3, 7, 2, 6, 6, 6, 4, 4, 6, 6, 4, 4, 3, 3, 6, 2, 5, 1, 6, 2, 6, 6, 4, 4, 6, 6, 4, 4, 6, 6, 4, 4, 2, 2, 4, 4, 4, 4, 1, 3, 4, 4, 3, 5, 6, 6, 4, 4, 2, 2, 4, 4, 4, 4, 3, 1, 4, 4, 5, 3, 3, 3, 6, 2, 1, 5, 6, 2, 2, 2, 4, 4, 2, 2, 4, 4, 5, 5, 2, 6, 3, 7, 2, 6, 2, 2, 4, 4, 2, 2, 4, 4, 6, 6, 4, 4

Offset

0,3

Links

Robert Israel, Table of n, a(n) for n = 0..10000

Formula

From Robert Israel, Sep 26 2018: (Start)

If A011371(n) == 0 (mod 3) then a(n) = A049606(n) mod 8.

If A011371(n) == 1 (mod 3) then a(n) = 2*(A049606(n) mod 4).

If A011371(n) == 2 (mod 3) then a(n) = 4. (End)

Example

6! = 720 decimal = 1320 octal, so a(6) = 2.

Maple

P:= 1: E:= 0: a[0]:= 1:
for n from 1 to 100 do
  v:= padic:-ordp(n, 2);
  P:= P*(n/2^v) mod 8;
  E:= E + v;
  if E mod 3 = 0 then a[n]:= P
  elif E mod 3 = 1 then a[n]:= 2*(P mod 4)
  else a[n]:= 4
  fi
od:
seq(a[n], n=0..100); # Robert Israel, Sep 26 2018

Crossrefs

Cf. A000142, A136690, A136691, A136692, A136693, A136694, A136696, A008904, A136697, A136698, A136699, A136700, A136701, A136702.

Cf. A011371, A049606.

Sequence in context: A280342 A275476 A185380 * A337115 A354372 A354111

Adjacent sequences: A136692 A136693 A136694 * A136696 A136697 A136698

Keyword

base,easy,nonn

Author

Carl R. White, Jan 16 2008

Status

approved