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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 (list; graph; refs; listen; history; text; internal format)
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.

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 * A168458 A165138 A196395

Adjacent sequences:  A100632 A100633 A100634 * A100636 A100637 A100638

KEYWORD

mult,easy,nonn,changed

AUTHOR

Vladeta Jovovic, Dec 03 2004

STATUS

approved

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Last modified May 29 22:45 EDT 2017. Contains 287257 sequences.