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A084776
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a(n) = sum of absolute-valued coefficients of (1+2x-x^2)^n.
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2
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1, 4, 12, 36, 100, 300, 776, 2412, 6304, 19036, 50952, 148896, 393452, 1211444, 3167004, 9672772, 25295248, 76084796, 200590424, 608621376, 1617201648, 4908511140, 12658776540, 38907904188, 102775961200, 310485090044
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OFFSET
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0,2
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LINKS
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Table of n, a(n) for n=0..25.
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PROG
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(PARI) for(n=0, 40, S=sum(k=0, 2*n, abs(polcoeff((1+2*x-x^2)^n, k, x))); print1(S", "))
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CROSSREFS
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Sequence in context: A191756 A001411 A095350 * A162921 A237045 A291732
Adjacent sequences: A084773 A084774 A084775 * A084777 A084778 A084779
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna, Jun 14 2003
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STATUS
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approved
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