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A033587
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a(n) = 2*n*(4*n + 3).
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11
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0, 14, 44, 90, 152, 230, 324, 434, 560, 702, 860, 1034, 1224, 1430, 1652, 1890, 2144, 2414, 2700, 3002, 3320, 3654, 4004, 4370, 4752, 5150, 5564, 5994, 6440, 6902, 7380, 7874, 8384, 8910, 9452, 10010, 10584, 11174, 11780, 12402, 13040, 13694, 14364, 15050
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OFFSET
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0,2
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COMMENTS
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The inverse binomial transform is [0, 14, 16, 0, 0, 0, ...]. - R. J. Mathar, May 06 2008
Sequence found by reading the line from 0, in the direction 0, 14, ..., in the square spiral whose vertices are the triangular numbers A000217. Opposite numbers to the even hexagonal numbers A014635 in the same spiral. - Omar E. Pol, Sep 03 2011
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LINKS
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FORMULA
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Sum_{n>=1} 1/a(n) = 2/9 + Pi/12 - log(2)/2.
Sum_{n>=1} (-1)^n/a(n) = 2/9 - Pi/(6*sqrt(2)) - log(2)/6 + log(1+sqrt(2))/(3*sqrt(2)). (End)
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MATHEMATICA
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LinearRecurrence[{3, -3, 1}, {0, 14, 44}, 80] (* Harvey P. Dale, Jun 05 2019 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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