A045564 Numbers whose factorial has '68' as its final two digits before the trailing zeros.

11, 15, 22, 27, 39, 70, 73, 89, 106, 149, 184, 191, 197, 221, 229, 274, 295, 298, 310, 318, 329, 354, 379, 430, 467, 474, 492, 505, 514, 540, 611, 655, 702, 706, 762, 810, 818, 832, 845, 848

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Index entries for sequences related to final digits of numbers

Mathematica

f2nzdQ[n_] := Mod[n!/10^IntegerExponent[n!, 10], 100] == 68; Select[ Range[ 900], f2nzdQ] (* Harvey P. Dale, Aug 14 2017 *)

Prog

(PARI) last(n, k)=if(n*8\9-1<k, n=n!; return(n/10^valuation(n, 10)%10^k)); my(m=Mod(1, 5^k)); for(i=2, n, m*=i/10^valuation(i, 5)); lift(chinese(m, Mod(0, 2^k))) \\ Gives the last k decimal digits of n!.
is(n)=last(n, 2)==68 \\ Charles R Greathouse IV, Oct 22 2014
(PARI) is(n)=my(m=Mod(1, 25)); for(i=2, n, m*=i/10^valuation(i, 5)); m==68 \\ Charles R Greathouse IV, Oct 22 2014
(PARI) v=List(); m=Mod(1, 25); for(n=2, 1e6, m*=n/10^valuation(n, 5); if(m==68, listput(v, n); if(#v==100, return(Vec(v))))) \\ Charles R Greathouse IV, Oct 22 2014

Crossrefs

Sequence in context: A211322 A087682 A104628 * A285271 A087142 A158019

Adjacent sequences: A045561 A045562 A045563 * A045565 A045566 A045567

Keyword

nonn,base

Author

Jeff Burch

Status

approved