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A106832
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4n-2 and 6n alternatively.
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1
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2, 6, 6, 12, 10, 18, 14, 24, 18, 30, 22, 36, 26, 42, 30, 48, 34, 54, 38, 60, 42, 66, 46, 72, 50, 78, 54, 84, 58, 90, 62, 96, 66, 102, 70, 108, 74, 114, 78, 120, 82, 126, 86, 132, 90, 138, 94, 144, 98, 150
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (0,2,0,-1).
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FORMULA
| a(n) = n*(3-mod(n, 2)).
Contribution from Bruno Berselli, Sep 26 2011: (Start)
G.f.: 2*x*(1+3*x+x^2))/(1-x^2)^2.
a(n) = (1/2)*((-1)^n+5)*n.
a(n) = -a(-n) = A195013(n)-A195013(-n). (End)
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MAPLE
| a:=n->add(2+add((-1)^j, j=2..n), j=1..n):seq(a(n), n=1..69); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 13 2008]
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PROG
| (MAGMA) &cat[[4*n-2, 6*n]: n in [1..25]]; // Bruno Berselli, Sep 26 2011
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CROSSREFS
| Sequence in context: A099027 A134466 A062562 * A129902 A087560 A071892
Adjacent sequences: A106829 A106830 A106831 * A106833 A106834 A106835
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KEYWORD
| nonn,easy
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), May 19 2005
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EXTENSIONS
| Definition corrected by Bruno Berselli, Sep 26 2011
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