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Search: id:A085490
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| A085490 |
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Number of pairs with two different elements which can be obtained by selecting unique elements from two sets with n+1 and n^2 elements respectively and n common elements. |
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+0
2
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| 0, 1, 10, 33, 76, 145, 246, 385, 568, 801, 1090, 1441, 1860, 2353, 2926, 3585, 4336, 5185, 6138, 7201, 8380, 9681, 11110, 12673, 14376, 16225, 18226, 20385, 22708, 25201, 27870
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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a(n) = n^3 + n^2 - n
a(n)=A081437(n-1), n>0. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 12 2008]
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EXAMPLE
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a(3)=10 because we can write a(3) = 2^3+2^2-2 = 10
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MAPLE
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a:=n->sum(n*k, k=0..n):seq(a(n)+sum(n*k, k=2..n), n=0...30); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 10 2008
a:=n->sum(-2+sum(2+sum(2, j=1..n), j=1..n), j=1..n):seq(a(n)/2, n=0..40); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 06 2008]
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CROSSREFS
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Sequence in context: A067877 A063160 A065149 this_sequence A081437 A162433 A003012
Adjacent sequences: A085487 A085488 A085489 this_sequence A085491 A085492 A085493
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KEYWORD
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nonn
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AUTHOR
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Polina.S.Dolmatova (polinasport((AT))mail.ru), Aug 15 2003
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