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Search: id:A050521
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| A050521 |
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Number of factorizations of (n,2*n) into pairs (k,l). |
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+0
1
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| 1, 1, 1, 3, 1, 7, 1, 10, 4, 7, 1, 33, 1, 7, 9, 28, 1, 39, 1, 33
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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Pairs (k,l) must satisfy 0<k, 0<l; if k=1 then l=1. Definition of "*": (a,b)*(x,y)=(a*x,b*y); unit is (1,1).
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EXAMPLE
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(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.
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CROSSREFS
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Cf. A051707.
Sequence in context: A099749 A077202 A086665 this_sequence A098093 A114712 A089741
Adjacent sequences: A050518 A050519 A050520 this_sequence A050522 A050523 A050524
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KEYWORD
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nonn,nice,easy,more
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AUTHOR
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Yasutoshi Kohmoto (zbi74583(AT)boat.zero.ad.jp)
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