

A100635


Number of 2 X 2 matrices with elements in {1,2,...,n} such that LCMs of rows and columns are n.


1



1, 7, 7, 17, 7, 49, 7, 31, 17, 49, 7, 119, 7, 49, 49, 49, 7, 119, 7, 119, 49, 49, 7, 217, 17, 49, 31, 119, 7, 343, 7, 71, 49, 49, 49, 289, 7, 49, 49, 217, 7, 343, 7, 119, 119, 49, 7, 343, 17, 119, 49, 119, 7, 217, 49, 217, 49, 49, 7, 833, 7, 49, 119
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OFFSET

1,2


LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000


FORMULA

Multiplicative with a(p^e) = 2*((e+1)^2)  1.


MATHEMATICA

Flatten[{1, Table[Product[2*((e+1)^2)  1, {e, FactorInteger[n][[All, 2]]}], {n, 2, 100}]}] (* Vaclav Kotesovec, Sep 20 2020 *)


PROG

(PARI) A100635(n) = { my(f = factor(n), m = 1); for (k=1, #f~, m *= (2*((f[k, 2]+1)^2))1; ); m; } \\ Antti Karttunen, May 25 2017


CROSSREFS

Cf. A048691.
Sequence in context: A120682 A152910 A198439 * A292084 A168458 A165138
Adjacent sequences: A100632 A100633 A100634 * A100636 A100637 A100638


KEYWORD

mult,easy,nonn


AUTHOR

Vladeta Jovovic, Dec 03 2004


STATUS

approved



