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Search: id:A080857
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| A080857 |
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Generalized polygonal numbers. |
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+0
2
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| 1, 6, 36, 91, 171, 276, 406, 561, 741, 946, 1176, 1431, 1711, 2016, 2346, 2701, 3081, 3486, 3916, 4371, 4851, 5356, 5886, 6441, 7021, 7626, 8256, 8911, 9591, 10296, 11026, 11781, 12561, 13366, 14196, 15051, 15931, 16836, 17766, 18721, 19701
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Row T(5,n) of A080853
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FORMULA
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a(n)=(25n^2-15n+2)/2 G.f.: (1+3x+21x^2)/(1-x)^3
a(n)=25*n+a(n-1)-45 (with a(1)=1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 17 2009]
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EXAMPLE
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For n=2, a(2)=25*2+1-45=6; n=3, a(3)=25*3+6-45=36; n=4, a(4)=25*4+36-45=91 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 17 2009]
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CROSSREFS
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Sequence in context: A043116 A044108 A152746 this_sequence A108158 A086113 A060521
Adjacent sequences: A080854 A080855 A080856 this_sequence A080858 A080859 A080860
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KEYWORD
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easy,nonn,new
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Feb 23 2003
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