This site is supported by donations to The OEIS Foundation.

 Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS". Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 * A292084 A168458 A165138 Adjacent sequences:  A100632 A100633 A100634 * A100636 A100637 A100638 KEYWORD mult,easy,nonn AUTHOR Vladeta Jovovic, Dec 03 2004 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified November 20 04:05 EST 2017. Contains 294959 sequences.