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A045549 Numbers n such that final nonzero digit of n! is '6'. 5
3, 12, 17, 24, 29, 32, 45, 46, 48, 59, 60, 61, 63, 65, 66, 68, 72, 79, 82, 95, 96, 98, 104, 107, 120, 121, 123, 127, 130, 131, 133, 139, 144, 159, 160, 161, 163, 165, 166, 168, 172, 175, 176, 178, 187, 192, 199, 209, 210, 211, 213, 215, 216, 218 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

From Robert Israel, Dec 16 2016: (Start)

If n is in the sequence, then:

if n == 0 (mod 5), n+1 is in the sequence;

if n == 1 (mod 5), n+1 is in A045547;

if n == 2 (mod 5), n+1 is in A045550;

if n == 3 (mod 5), n+1 is in A045548. (End)

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

Index entries for sequences related to final digits of numbers

MAPLE

count:= 0:

r:= 1:

for n from 2 while count < 100 do

  r:= r*n;

  if r mod 10 = 0 then r:= r/10^padic:-ordp(r, 5) fi;

  if r mod 10 = 6 then count:= count+1; A[count]:= n fi;

od:

seq(A[i], i=1..100); # Robert Israel, Dec 16 2016

MATHEMATICA

Join[{3}, Select[Range[5, 250], Most[Split[IntegerDigits[#!]]][[-1, 1]] == 6 &]] (* Vincenzo Librandi, Dec 16 2016 *)

f[n_] := Mod[6 Times @@ (Rest[ FoldList[{1 + #1[[1]], #2! 2^(#1[[1]] #2)} &, {0, 0}, Reverse[ IntegerDigits[n, 5]]]]), 10][[2]] (* after Jacob A. Siehler & Greg Dresden in A008904 *); f[0] = f[1] = 1; Select[ Range[150], f[#] == 6 &] (* Robert G. Wilson v, Dec 28 2016 *)

CROSSREFS

Cf. A008904, A045547, A045548, A045550.

Sequence in context: A224924 A136047 A082965 * A103249 A047906 A104641

Adjacent sequences:  A045546 A045547 A045548 * A045550 A045551 A045552

KEYWORD

nonn,base

AUTHOR

Jeff Burch

STATUS

approved

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Last modified August 4 08:14 EDT 2020. Contains 336201 sequences. (Running on oeis4.)