

A205561


Least positive integer k such that n divides (2k)!(2j)! for some j in [1,k1].


1



2, 2, 3, 3, 4, 3, 5, 3, 4, 4, 2, 3, 8, 5, 4, 4, 10, 4, 4, 4, 5, 2, 4, 3, 4, 8, 6, 5, 3, 4, 5, 5, 4, 10, 5, 4, 20, 4, 8, 4, 11, 5, 10, 4, 4, 4, 5, 4, 6, 4, 10, 8, 6, 6, 4, 5, 8, 3, 13, 4, 8, 5, 5, 5, 8, 4, 16, 10, 4, 5, 7, 4, 4, 20, 4, 8, 7, 8, 11, 4, 6, 11, 22, 5, 10, 10, 3, 4, 5, 4, 8, 4
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OFFSET

1,1


COMMENTS

For a guide to related sequences, see A204892.


LINKS



EXAMPLE

1 divides (2*2)!(2*1)! > k=2, j=1
2 divides (2*2)!(2*1)! > k=2, j=1
3 divides (2*3)!(2*2)! > k=3, j=2
4 divides (2*3)!(2*2)! > k=3, j=2
5 divides (2*4)!(2*3)! > k=4, j=3


MATHEMATICA

s = Table[(2n)!, {n, 1, 120}];
lk = Table[NestWhile[# + 1 &, 1,
Min[Table[Mod[s[[#]]  s[[j]], z], {j, 1, #  1}]] =!= 0 &], {z, 1, Length[s]}]
Table[NestWhile[# + 1 &, 1,
Mod[s[[lk[[j]]]]  s[[#]], j] =!= 0 &],
{j, 1, Length[lk]}]


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



