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A084780 a(n) = sum of absolute-valued coefficients of (1+3x-x^2)^n. 2
1, 5, 21, 77, 291, 1119, 3523, 15007, 50923, 182669, 701121, 2379129, 8909361, 32490021, 106309861, 423990203, 1456199483, 5089398187, 19942506259, 65753622619, 252337832801, 903751067081, 3026099773993, 11771846189609 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..23.

MATHEMATICA

Table[Total[Abs[CoefficientList[Expand[(1+3x-x^2)^n], x]]], {n, 0, 30}] (* Harvey P. Dale, Jan 04 2012 *)

PROG

(PARI) for(n=0, 40, S=sum(k=0, 2*n, abs(polcoeff((1+3*x-x^2)^n, k, x))); print1(S", "))

CROSSREFS

Sequence in context: A255453 A134770 A272787 * A268202 A055219 A108863

Adjacent sequences:  A084777 A084778 A084779 * A084781 A084782 A084783

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jun 14 2003

STATUS

approved

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Last modified July 10 15:45 EDT 2020. Contains 335577 sequences. (Running on oeis4.)