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Search: id:A016061
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| 0, 3, 13, 34, 70, 125, 203, 308, 444, 615, 825, 1078, 1378, 1729, 2135, 2600, 3128, 3723, 4389, 5130, 5950, 6853, 7843, 8924, 10100, 11375, 12753, 14238, 15834, 17545, 19375, 21328, 23408, 25619, 27965, 30450, 33078, 35853, 38779, 41860
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Number of ZnS molecules in cluster of n layers in zinc blend crystal.
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REFERENCES
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T. P. Martin, Shells of atoms, Phys. Reports, 273 (1996), 199-241, see p. 233.
G. Olive, Problem #504, Factorizations and Sums, Two-Year College Math. Jnl., 25 (1994), 244-245.
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FORMULA
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G.f.: x(3+x)/(1-x)^4 - Paul Barry (pbarry(AT)wit.ie), Feb 27 2003
Partial sums of n even triangular numbers, e.g. a(3)=t(0)+t(2)+t(4)=0+3+10=13 - Jon Perry (perry(AT)globalnet.co.uk), Jul 23 2003
a(n) = sum(i=0, n-1, 2*i^2 + i) - Jani Nurminen (slinky(AT)iki.fi), May 14 2006
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MAPLE
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seq(add((n^2-k^2), k=1..n), n=1..40); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 01 2006
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PROGRAM
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(PARI) v=vector(40, i, t(i)); s=0; forstep(i=2, 40, 2, s+=v[i]; print1(s", "))
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CROSSREFS
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Bisection of A002623.
Cf. A002412.
Row sums of triangle A120070.
Sequence in context: A032586 A033943 A026084 this_sequence A137976 A095661 A058214
Adjacent sequences: A016058 A016059 A016060 this_sequence A016062 A016063 A016064
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com)
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