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A216149 Numbers k such that Sum_{j=1..k-1} (3*j)!/5^j is an integer. 0
1, 3, 16 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The next term, if it exists, is greater than 1000000. - Vaclav Kotesovec, Sep 11 2012

LINKS

Table of n, a(n) for n=1..3.

MATHEMATICA

seq={}; sum=0; fak=1; k=0; While[k<10000, sum+=fak; If[Denominator[sum]==1, AppendTo[seq, k+1]]; k++; fak*=3*k*(3*k-1)*(3*k-2)/5; ]; seq

Select[Range[20], IntegerQ[Sum[(3k)!/5^k, {k, #-1}]]&] (* Harvey P. Dale, Apr 07 2019 *)

CROSSREFS

Cf. A215972, A216042, A216043, A216044, A216045.

Sequence in context: A290610 A134807 A004002 * A194604 A078355 A107823

Adjacent sequences:  A216146 A216147 A216148 * A216150 A216151 A216152

KEYWORD

nonn,more,bref

AUTHOR

Vaclav Kotesovec, Sep 02 2012

STATUS

approved

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Last modified July 26 13:40 EDT 2021. Contains 346294 sequences. (Running on oeis4.)