cp's OEIS Frontend

A045563 Numbers whose factorial has '64' as its final two digits before the trailing zeros.

%I A045563 #14 Jun 22 2021 01:03:23
%S A045563 20,23,92,99,100,101,143,156,195,198,208,219,227,230,268,280,327,331,
%T A045563 352,355,377,415,449,497,500,501,560,568,596,607,632,653,681,689,749,
%U A045563 761,765,772,783,794,856,902,914,932,946,964,1005,1014,1035,1085,1097
%N A045563 Numbers whose factorial has '64' as its final two digits before the trailing zeros.
%H A045563 Charles R Greathouse IV, <a href="/A045563/b045563.txt">Table of n, a(n) for n = 1..10000</a>
%H A045563 <a href="/index/Fi#final">Index entries for sequences related to final digits of numbers</a>
%o A045563 (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!.
%o A045563 is(n)=last(n,2)==64 \\ _Charles R Greathouse IV_, Oct 22 2014
%o A045563 (PARI) is(n)=my(m=Mod(1,25)); for(i=2,n, m*=i/10^valuation(i,5)); m==64 \\ _Charles R Greathouse IV_, Oct 22 2014
%o A045563 (PARI) v=List();m=Mod(1,25);for(n=2,1e6,m*=n/10^valuation(n,5);if(m==64,listput(v,n);if(#v==100, return(Vec(v))))) \\ _Charles R Greathouse IV_, Oct 22 2014
%K A045563 nonn,base
%O A045563 1,1
%A A045563 _Jeff Burch_
%E A045563 More terms from _Robert G. Wilson v_, Dec 14 2000