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Search: id:A140090
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| 0, 5, 13, 24, 38, 55, 75, 98, 124, 153, 185, 220, 258, 299, 343, 390, 440, 493, 549, 608, 670, 735, 803, 874, 948, 1025, 1105, 1188, 1274, 1363, 1455, 1550, 1648, 1749, 1853, 1960, 2070, 2183, 2299, 2418, 2540, 2665, 2793, 2924
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OFFSET
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0,2
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FORMULA
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a(n)=(3*n^2 + 7*n)/2.
a(n)=3*n+a(n-1)-1 (with a(1)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 08 2009]
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EXAMPLE
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For n=2, a(2)=3*2+0-1=5; n=3, a(3)=3*3+5-1=13; n=4, a(4)=3*4+13-1=24 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 08 2009]
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MATHEMATICA
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s=-1; lst={}; Do[s+=n+n+n-1; If[s>=0, AppendTo[lst, s]], {n, 0, 6!, 1}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Nov 04 2008]
Table[Sum[i + n - 3, {i, 4, n}], {n, 3, 50}] [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 11 2009]
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CROSSREFS
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Cf. A000326, A005449, A045943, A115067, A140091, A059845, A140672, A140673, A140674, A140675.
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: A075829 A119248 A114998 this_sequence A121511 A156679 A004627
Adjacent sequences: A140087 A140088 A140089 this_sequence A140091 A140092 A140093
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KEYWORD
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easy,nonn
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AUTHOR
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Omar E. Pol (info(AT)polprimos.com), May 22 2008
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