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A033568
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Second pentagonal numbers with odd index: (2*n-1)*(3*n-1).
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10
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1, 2, 15, 40, 77, 126, 187, 260, 345, 442, 551, 672, 805, 950, 1107, 1276, 1457, 1650, 1855, 2072, 2301, 2542, 2795, 3060, 3337, 3626, 3927, 4240, 4565, 4902, 5251, 5612, 5985, 6370, 6767, 7176, 7597, 8030, 8475, 8932, 9401, 9882, 10375, 10880, 11397, 11926
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Sequence found by reading the segment (1, 2) together with the line (one of the diagonal axes) from 2, in the direction 2, 15,..., in the square spiral whose vertices are the generalized pentagonal numbers A001318. - Omar E. Pol, Sep 08 2011
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LINKS
| Index entries for sequences related to linear recurrences with constant coefficients, signature (3,-3,1).
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FORMULA
| G.f.: A(x) = (1-x+12*x^2)/(1-x)^3.
a(n)=a(n-1)+12*n-11 (with a(0)=1) [From Vincenzo Librandi, Nov 17 2010]
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MATHEMATICA
| Table[(2*n-1)*(3*n-1), {n, 0, 5!}] [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Apr 28 2010]
LinearRecurrence[{3, -3, 1}, {1, 2, 15}, 46]
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CROSSREFS
| Cf. A005449, A049453, A033570.
Cf. A001318, A049452. - Omar E. Pol, Sep 08 2011
Sequence in context: A180223 A070009 A070170 * A200156 A032016 A001007
Adjacent sequences: A033565 A033566 A033567 * A033569 A033570 A033571
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 08 2011
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