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A045553 Numbers n such that final 2 nonzero digits of n! are '12'. 1
5, 14, 38, 43, 47, 50, 51, 88, 90, 111, 129, 153, 242, 254, 275, 276, 292, 367, 387, 420, 423, 436, 454, 496, 513, 530, 570, 573, 577, 581, 608, 614, 619, 633, 644, 660, 699, 710, 722, 743, 771, 787, 799, 825, 826, 837 (list; graph; refs; listen; history; text; internal format)
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)==12 \\ 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==12 \\ 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==12, listput(v, n); if(#v==100, return(Vec(v))))) \\ Charles R Greathouse IV, Oct 22 2014

CROSSREFS

Sequence in context: A054486 A072130 A196976 * A270687 A272254 A270452

Adjacent sequences:  A045550 A045551 A045552 * A045554 A045555 A045556

KEYWORD

nonn,base

AUTHOR

Jeff Burch

STATUS

approved

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Last modified November 14 09:51 EST 2019. Contains 329111 sequences. (Running on oeis4.)