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URL: https://oeis.org/A045564

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A045564
Numbers whose factorial has '68' as its final two digits before the trailing zeros.
1
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
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
KEYWORD
nonn,base
AUTHOR
STATUS
approved