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A132769
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a(n) = n*(n + 27).
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5
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0, 28, 58, 90, 124, 160, 198, 238, 280, 324, 370, 418, 468, 520, 574, 630, 688, 748, 810, 874, 940, 1008, 1078, 1150, 1224, 1300, 1378, 1458, 1540, 1624, 1710, 1798, 1888, 1980, 2074, 2170, 2268, 2368, 2470, 2574, 2680, 2788, 2898, 3010, 3124, 3240, 3358, 3478
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OFFSET
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0,2
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LINKS
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FORMULA
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a(0)=0, a(1)=28, a(2)=58; for n>2, a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - Harvey P. Dale, Oct 14 2012
Sum_{n>=1} 1/a(n) = H(27)/27 = A001008(27)/A102928(27) = 312536252003/2168462696400, where H(k) is the k-th harmonic number.
Sum_{n>=1} (-1)^(n+1)/a(n) = 2*log(2)/27 - 57128792093/2168462696400. (End)
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MATHEMATICA
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Table[n(n+27), {n, 0, 50}] (* or *) LinearRecurrence[{3, -3, 1}, {0, 28, 58}, 50] (* Harvey P. Dale, Oct 14 2012 *)
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PROG
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CROSSREFS
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Cf. A001008, A002378, A102928, A120071, A132760, A132761, A132762, A132763, A132764, A132765, A132766, A132767, A132768, A098849, A098850, A005563, A028552, A028347, A028557, A028560, A028563, A028566, A028569, A098603, A098847, A132759, A098848.
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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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