A050521 Number of factorizations of (n,2*n) into pairs (k,l).

1, 1, 1, 3, 1, 7, 1, 10, 4, 7, 1, 33, 1, 7, 9, 28, 1, 39, 1, 33, 9, 7, 1, 133, 4, 7, 15, 33, 1, 91, 1, 80, 9, 7, 9, 229, 1, 7, 9, 133, 1, 91, 1, 33, 53, 7, 1, 474, 4, 39, 9, 33, 1, 175, 9, 133, 9, 7, 1, 569, 1, 7, 53, 208, 9, 91, 1, 33, 9, 91, 1

Offset: 1

Author

Yasutoshi Kohmoto

Keywords

• nonn
• nice
• easy

Comments

Pairs (k,l) must satisfy 0

Factorization is up to ordering of pairs, thus (2,2)*(5,10) is the same as (5,10)*(2,2). Factorizations may involve an arbitrary number of pairs, (2,2)*(3,4)*(5,6)=(30,48). - Sean A. Irvine, Mar 21 2013

Examples

			(10,20) = (2,1)*(5,20) = (2,20)*(5*1) = (2,2)*(5,10) = (2,10)*(5,2) = (2,4)*(5,5) = (2,5)*(5,4); so a(10) = 7.
		

Links

• Giovanni Resta, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A051707.

Extensions

More terms from Sean A. Irvine, Mar 21 2013

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