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A218471
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a(n) = n*(7*n-3)/2.
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9
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0, 2, 11, 27, 50, 80, 117, 161, 212, 270, 335, 407, 486, 572, 665, 765, 872, 986, 1107, 1235, 1370, 1512, 1661, 1817, 1980, 2150, 2327, 2511, 2702, 2900, 3105, 3317, 3536, 3762, 3995, 4235, 4482, 4736, 4997, 5265, 5540, 5822, 6111, 6407, 6710, 7020, 7337
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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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G.f.: x*(2+5*x)/(1-x)^3.
a(n) = 3*a(n-1) -3*a(n-2) +a(n-3) with a(0)=0, a(1)=2, a(2)=11.
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MAPLE
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MATHEMATICA
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PROG
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(Magma) [n*(7*n-3)/2: n in [0..50]]; // G. C. Greubel, Aug 31 2019
(Sage) [n*(7*n-3)/2 for n in (0..50)] # G. C. Greubel, Aug 31 2019
(GAP) List([0..50], n-> n*(7*n-3)/2); # G. C. Greubel, Aug 31 2019
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CROSSREFS
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Cf. numbers of the form n*(n*k-k+4))/2 listed in A226488 (this sequence is the case k=7). - Bruno Berselli, Jun 10 2013
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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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