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A054776
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a(n) = 3*n*(3*n-1)*(3*n-2).
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5
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0, 6, 120, 504, 1320, 2730, 4896, 7980, 12144, 17550, 24360, 32736, 42840, 54834, 68880, 85140, 103776, 124950, 148824, 175560, 205320, 238266, 274560, 314364, 357840, 405150, 456456, 511920, 571704, 635970, 704880, 778596, 857280, 941094
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OFFSET
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0,2
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REFERENCES
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L. B. W. Jolley, "Summation of Series", Dover Publications, 1961, p. 46.
Konrad Knopp, Theory and Application of Infinite Series, Dover, p. 268.
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LINKS
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FORMULA
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Sum_{n>=1} 1/a(n) = Pi*sqrt(3)/12 - log(3)/4 = 0.178796768891527... [Jolley eq. 250]. - Benoit Cloitre, Apr 05 2002
G.f.: 6*x*(1+16*x+10*x^2)/(1-x)^4.
Sum_{n>=1} (-1)^(n+1)/a(n) = 2*log(2)/3 - Pi/(6*sqrt(3)). - Amiram Eldar, Mar 08 2022
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MAPLE
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PROG
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(PARI) a(n)=3*n*(3*n-1)*(3*n-2)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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