A045556 Numbers whose factorial has '28' as its final two digits before the trailing zeros.

18, 33, 44, 57, 71, 102, 105, 128, 170, 173, 188, 204, 253, 296, 309, 316, 322, 382, 453, 499, 502, 538, 543, 547, 588, 590, 622, 638, 705, 733, 739, 744, 774, 809, 816, 822, 846, 854, 892, 936, 957, 970, 973, 995, 998, 1004, 1055, 1092, 1099, 1117, 1131

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

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)==28 \\ 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==28 \\ 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==28, listput(v, n); if(#v==100, return(Vec(v))))) \\ Charles R Greathouse IV, Oct 22 2014

Crossrefs

Sequence in context: A137600 A299707 A350958 * A344017 A049731 A188212

Adjacent sequences: A045553 A045554 A045555 * A045557 A045558 A045559

Keyword

nonn,base

Author

Jeff Burch

Extensions

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

Status

approved