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Search: id:A073014
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| A073014 |
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(n!/2)*sum(k=1,n,(n+k)!/(k!)^3). |
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+0
1
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| 1, 9, 127, 2835, 93901, 4336878, 266268402, 20961918435, 2057633544961, 246291719185578, 35300219800649134, 5967365133741366446, 1174674087014062487490, 266337973265724541242428
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OFFSET
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1,2
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COMMENT
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a(n) is odd for n = 1,2,3 and if n is of the form 2^m or 2^m+1 (with m>= 2) (i.e. a(n) is odd if n=1,3,4,5,8,9,16,17,32,33,64,65,128,129,256,257...)
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PROGRAM
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(PARI) a(n)=if(n<0, 0, (n!/2)*sum(k=1, n, (n+k)!/(k!)^3))
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CROSSREFS
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Sequence in context: A065707 A034301 A092651 this_sequence A046754 A064746 A075762
Adjacent sequences: A073011 A073012 A073013 this_sequence A073015 A073016 A073017
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KEYWORD
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easy,nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 03 2002
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