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Search: id:A085789
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| A085789 |
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Partial sums of n 3-spaced triangular numbers beginning with t(2), e.g. a(2)=t(2)+t(5)=3+15=18. |
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+0
2
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| 3, 18, 54, 120, 225, 378, 588, 864, 1215, 1650, 2178, 2808, 3549, 4410, 5400, 6528, 7803, 9234, 10830, 12600, 14553, 16698, 19044, 21600, 24375, 27378, 30618, 34104, 37845, 41850, 46128, 50688, 55539, 60690, 66150, 71928, 78033, 84474, 91260
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Sums of rows of triangle A100345 (n>0).
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FORMULA
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3/2 * n^2(n+1).
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MAPLE
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seq(add((n^2-k^2+(n+k)^2)/2, k=0..n), n=1..39); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 01 2006
a:=n->sum ((j+n+1)*n, j=1..n): seq(a(n), n=1..39); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 17 2006
restart: a:=n->sum(sum(k, j=3..n), k=0..n): seq(a(n), n=1..53):b:=n->sum(sum(n, j=0..n), k=0..n): seq(a(n), n=1..53):c:=b+a:seq(c(n), n=1..39); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 24 2008]
a:=n->add(binomial(n, 2)+add(n, j=2..n), j=2..n):seq(a(n), n=2..40); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 27 2008]
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PROGRAM
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(PARI) v=vector(40, i, t(i)); s=0; forstep(i=2, 40, 3, s+=v[i]; print1(s", "))
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CROSSREFS
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Cf. A004188.
Sequence in context: A094159 A138976 A064043 this_sequence A027334 A130505 A027289
Adjacent sequences: A085786 A085787 A085788 this_sequence A085790 A085791 A085792
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KEYWORD
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nonn
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AUTHOR
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Jon Perry (perry(AT)globalnet.co.uk), Jul 23 2003
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EXTENSIONS
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More terms from Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Nov 18 2004
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