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A152744
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7 times pentagonal numbers: 7n(3n-1)/2.
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2
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0, 7, 35, 84, 154, 245, 357, 490, 644, 819, 1015, 1232, 1470, 1729, 2009, 2310, 2632, 2975, 3339, 3724, 4130, 4557, 5005, 5474, 5964, 6475, 7007, 7560, 8134, 8729, 9345, 9982, 10640, 11319, 12019, 12740, 13482, 14245, 15029
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| a(n) = (21n^2 - 7n)/2 = A000326(n)*7.
a(n)=a(n-1)+21*n-14 (with a(0)=0). [From Vincenzo Librandi, Nov 26 2010]
G.f.: 7*x*(1+2*x)/(1-x)^3. [Colin Barker, Feb 14 2012]
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MATHEMATICA
| s=0; lst={s}; Do[s+=n; AppendTo[lst, s], {n, 7, 7!, 21}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Apr 03 2009]
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CROSSREFS
| Cf. A000326, A014642, A152743.
Sequence in context: A000829 A061825 A077536 * A169607 A130884 A037092
Adjacent sequences: A152741 A152742 A152743 * A152745 A152746 A152747
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KEYWORD
| easy,nonn,changed
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AUTHOR
| Omar E. Pol (info(AT)polprimos.com), Dec 12 2008
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