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Search: id:A111694
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| A111694 |
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a(1) = 1+2-3 = 0, a(2) = 4+5+6-7 = 8, a(3) = 8+9+10+11-12 = 26, a(4) = 13+14+15+16+17-18 = 57, ... |
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1
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| 0, 8, 26, 57, 104, 170, 258, 371, 512, 684, 890, 1133, 1416, 1742, 2114, 2535, 3008, 3536, 4122, 4769, 5480, 6258, 7106, 8027, 9024, 10100, 11258, 12501, 13832, 15254, 16770, 18383, 20096, 21912, 23834, 25865, 28008, 30266, 32642, 35139, 37760
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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(n^3 + 4n^2 - 3n - 2)/2.
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MAPLE
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seq(sum(j, j=binomial(n+1, 2)+n-1..binomial(n+2, 2)+n-2) - binomial(n+2, 2)-n+1, n=1..50); (Deutsch)
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MATHEMATICA
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Table[(n^3 + 4n^2 - 3n - 2)/2, {n, 41}] (* Robert G. Wilson v *)
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CROSSREFS
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Cf. A034856.
Adjacent sequences: A111691 A111692 A111693 this_sequence A111695 A111696 A111697
Sequence in context: A126264 A085690 A005897 this_sequence A129111 A002413 A002901
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 17 2005
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EXTENSIONS
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Edited and extended by Emeric Deutsch (deutsch(AT)duke.poly.edu) and Robert G. Wilson v (rgwv(at)rgwv.com), Aug 27 2005
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