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A103832
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For even n, a(n)=2n+1, for odd n, a(n)=n(n+1)
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1
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1, 2, 5, 12, 9, 30, 13, 56, 17, 90, 21, 132, 25, 182, 29, 240, 33, 306, 37, 380, 41, 462, 45, 552, 49, 650, 53, 756, 57, 870, 61, 992, 65, 1122, 69, 1260, 73, 1406, 77, 1560, 81, 1722, 85, 1892, 89, 2070, 93, 2256, 97, 2450, 101, 2652, 105, 2862, 109, 3080, 113
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| First the sum then the product of two successive integers.
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (0,3,0,-3,0,1).
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FORMULA
| G.f.: (1+3x^2)(1+2x-x^2)/((1-x)^3*(1+x)^3). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 30 2008]
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EXAMPLE
| a(4)=4+5=9, a(5)=5*6=30.
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MATHEMATICA
| Flatten[Table[{i + i + 1, (i + 1)(i + 2)}, {i, 0, 98, 2}]]
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CROSSREFS
| Cf. A103831.
Sequence in context: A110020 A070266 A125199 * A191368 A085227 A039586
Adjacent sequences: A103829 A103830 A103831 * A103833 A103834 A103835
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KEYWORD
| nonn
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Feb 17 2005, Feb 18 2005
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Aug 29 2008 at the suggestion of R. J. Mathar
Corrected typo in the definition - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 07 2010
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