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A085788
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Partial sums of n 3-spaced triangular numbers beginning with t(3), e.g. a(2)=t(3)+t(6)=6+21=27.
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1
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6, 27, 72, 150, 270, 441, 672, 972, 1350, 1815, 2376, 3042, 3822
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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FORMULA
| 3/2 * n(n+1)^2.
sum ((j+n+1)*(n+1),j=1..n). - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Sep 10 2006
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MAPLE
| a:=n->sum(sum(sum(j-k+1, j=1..n), k=0..n), m=0..n): seq(a(n), n=1..45); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 30 2007
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PROG
| (PARI) v=vector(40, i, t(i)); s=0; forstep(i=3, 40, 3, s+=v[i]; print1(s", "))
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CROSSREFS
| Cf. A004188.
Row sums of triangle A001283. Equals 3*A006002(n).
Sequence in context: A012365 A167469 A190623 * A027276 A101970 A136105
Adjacent sequences: A085785 A085786 A085787 * A085789 A085790 A085791
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KEYWORD
| nonn
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AUTHOR
| Jon Perry (perry(AT)globalnet.co.uk), Jul 23 2003
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