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A140675
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n*(3*n + 19)/2.
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13
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0, 11, 25, 42, 62, 85, 111, 140, 172, 207, 245, 286, 330, 377, 427, 480, 536, 595, 657, 722, 790, 861, 935, 1012, 1092, 1175, 1261, 1350, 1442, 1537, 1635, 1736, 1840, 1947, 2057, 2170, 2286, 2405, 2527, 2652, 2780, 2911, 3045, 3182
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| a(n)=(3*n^2 + 19*n)/2.
a(n)=3*n+a(n-1)+8 (with a(0)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 03 2010]
G.f.: x*(11 - 8*x)/(1 - x)^3. [Arkadiusz Wesolowski, Dec 24 2011]
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EXAMPLE
| a(1)=3*1+0+8=11; a(2)=3*2+11+8=25; a(3)=3*3+25+8=42 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 03 2010]
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MATHEMATICA
| s=0; lst={s}; Do[s+=n++ +11; AppendTo[lst, s], {n, 0, 7!, 3}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Nov 19 2008]
Table[Sum[i + n - 3, {i, 7, n}], {n, 6, 52}] [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 11 2009]
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CROSSREFS
| Cf. A000326, A005449, A045943, A115067, A140090, A140091, A059845, A140672, A140673, A140674.
The generalized pentagonal numbers b*n+3*n*(n-1)/2, for b = 1 through 12, form sequences A000326, A005449, A045943, A115067, A140090, A140091, A059845, A140672, A140673, A140674, A140675, A151542.
Sequence in context: A084547 A125868 A031025 * A161532 A118648 A105270
Adjacent sequences: A140672 A140673 A140674 * A140676 A140677 A140678
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KEYWORD
| easy,nonn
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AUTHOR
| Omar E. Pol (info(AT)polprimos.com), May 22 2008
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