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A071619
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If n mod 3 = 0 then 6*(n/3)^2 elif n mod 3 = 1 then 6*((n-1)/3)^2+4*(n-1)/3+1 else 6*((n-2)/3)^2+8*(n-2)/3 +3.
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4
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0, 1, 3, 6, 11, 17, 24, 33, 43, 54, 67, 81, 96, 113, 131, 150, 171, 193, 216, 241, 267, 294, 323, 353, 384, 417, 451, 486, 523, 561, 600, 641, 683, 726, 771, 817, 864, 913, 963, 1014, 1067, 1121, 1176, 1233, 1291, 1350, 1411, 1473, 1536, 1601, 1667, 1734, 1803, 1873
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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LINKS
| S. Lafortune, A. Ramani, B. Grammaticos, Y. Ohta and K.M. Tamizhmani, Blending two discrete integrability criteria: ...
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FORMULA
| a(n) = 2/3*n^2 if n mod 3 = 0 else 2/3*n^2+1/3. Recurrence: a(n) = 2*a(n-1)-a(n-2)+a(n-3)-2*a(n-4)+a(n-5). G.f.: x*(1+x)*(1+x^2)/(1+x+x^2)/(1-x)^3. - Vladeta Jovovic (vladeta(AT)eunet.rs), Jun 23 2002
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MAPLE
| A071619 := proc(n) if n mod 3 = 0 then 6*(n/3)^2 elif n mod 3 = 1 then 6*((n-1)/3)^2+4*(n-1)/3+1 else 6*((n-2)/3)^2+8*(n-2)/3 +3; fi; end;
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CROSSREFS
| Partial sums of A042968.
Sequence in context: A174648 A178419 A065504 * A025735 A023601 A173143
Adjacent sequences: A071616 A071617 A071618 * A071620 A071621 A071622
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jun 21 2002
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