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A084776 a(n) = sum of absolute-valued coefficients of (1+2x-x^2)^n. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..25.

PROG

(PARI) for(n=0, 40, S=sum(k=0, 2*n, abs(polcoeff((1+2*x-x^2)^n, k, x))); print1(S", "))

CROSSREFS

Sequence in context: A191756 A001411 A095350 * A162921 A237045 A291732

Adjacent sequences: A084773 A084774 A084775 * A084777 A084778 A084779

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jun 14 2003

STATUS

approved

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Last modified February 1 21:11 EST 2023. Contains 359997 sequences. (Running on oeis4.)