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Search: id:A098931
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| A098931 |
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a(n)=1+2*3+4*5+6*7+.... |
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+0
1
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| 1, 7, 27, 69, 141, 251, 407, 617, 889, 1231, 1651, 2157, 2757, 3459, 4271, 5201, 6257, 7447, 8779, 10261, 11901, 13707, 15687, 17849, 20201, 22751, 25507, 28477, 31669, 35091, 38751, 42657, 46817, 51239, 55931, 60901, 66157, 71707, 77559, 83721
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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If a(n)=a0,a1,a2,a3... then Sum(a(n))=a0,a0+a1,a0+a1+a2,a0+a1+a2+a3...
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FORMULA
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a(n)=1+3*n^2+n*(5+4*n^2)/3 G.f.: (1+3*x+5*x^2-x^3)/(1-x)^4
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EXAMPLE
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a(0)=1, a(1)=1+2*3=7, a(2)=1+2*3+4*5=27, etc.
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MATHEMATICA
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Table[1 + 3*n^2 + n(5 + 4n^2)/3, {n, 0, 40}] (from Robert G. Wilson v Oct 23 2004)
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CROSSREFS
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Cf. A068377.
Sequence in context: A015873 A022271 A159065 this_sequence A143690 A007715 A161439
Adjacent sequences: A098928 A098929 A098930 this_sequence A098932 A098933 A098934
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KEYWORD
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easy,nonn
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AUTHOR
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Miklos Kristof (kristmikl(AT)freemail.hu), Oct 20 2004
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EXTENSIONS
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Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 23 2004
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