A045551 Numbers whose factorial has '04' as its final two digits before the trailing zeros.

7, 28, 56, 64, 124, 138, 152, 164, 214, 233, 239, 244, 263, 283, 294, 304, 358, 364, 369, 381, 459, 466, 484, 488, 491, 524, 529, 532, 561, 604, 646, 703, 737, 804, 830, 893, 905, 952, 956, 977, 980, 1008, 1019, 1034, 1036, 1041, 1050, 1051, 1086, 1093

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

f[ n_Integer, m_Integer ] := (c = 0; p = 1; While[ d = Floor[ n/5^p ]; d > 0, c = c + d; p++ ]; Mod[ n!/10^c, m ] ); Select[ Range[ 250 ], f[ #, 100 ] == 4 & ]

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)==4 \\ 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==4 \\ 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==4, listput(v, n); if(#v==100, return(Vec(v))))) \\ Charles R Greathouse IV, Oct 22 2014

Crossrefs

Sequence in context: A068206 A118120 A078307 * A024844 A230285 A033582

Adjacent sequences: A045548 A045549 A045550 * A045552 A045553 A045554

Keyword

nonn,base

Author

Jeff Burch

Extensions

More terms from Robert G. Wilson v, Dec 14 2000

Status

approved