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URL: https://oeis.org/A045552

⇱ A045552 - OEIS

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A045552
Numbers whose factorial has '08' as its final two digits before the trailing zeros.
1
13, 80, 108, 114, 119, 137, 185, 193, 207, 220, 223, 246, 262, 315, 346, 371, 396, 400, 401, 417, 431, 439, 487, 506, 535, 550, 551, 585, 597, 609, 613, 616, 634, 635, 641, 656, 679, 708, 719, 767, 779, 782, 815
OFFSET
1,1
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)==8 \\ 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==8 \\ 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==8, listput(v, n); if(#v==100, return(Vec(v))))) \\ Charles R Greathouse IV, Oct 22 2014
CROSSREFS
Sequence in context: A236952 A136373 A071614 * A264381 A339851 A297678
KEYWORD
nonn,base
AUTHOR
STATUS
approved