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A045562 Numbers n such that final 2 nonzero digits of n! are '56'. 1
61, 96, 130, 139, 159, 161, 166, 178, 187, 192, 211, 218, 236, 255, 264, 324, 334, 341, 361, 388, 406, 432, 446, 458, 469, 483, 489, 494, 507, 537, 549, 555, 575, 576, 587, 624, 637, 654, 657, 684, 691, 697, 746, 756, 788, 793, 797, 824, 838, 840 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Index entries for sequences related to final digits of numbers

MATHEMATICA

lnzQ[n_]:=Module[{idn=IntegerDigits[n!], lz}, lz=Length[Last[Split[idn]]]; Take[idn, {-2-lz, -1-lz}]=={5, 6}]; Select[Range[10, 850], lnzQ] (* Harvey P. Dale, Mar 05 2013 *)

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)==56 \\ 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==56 \\ 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==56, listput(v, n); if(#v==100, return(Vec(v))))) \\ Charles R Greathouse IV, Oct 22 2014

CROSSREFS

Sequence in context: A309180 A038856 A144970 * A104229 A088787 A020350

Adjacent sequences:  A045559 A045560 A045561 * A045563 A045564 A045565

KEYWORD

nonn,base

AUTHOR

Jeff Burch

STATUS

approved

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Last modified November 14 02:19 EST 2019. Contains 329108 sequences. (Running on oeis4.)