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 A084615 a(n) = sum of absolute values of coefficients of (1+x-3x^2)^n. 18
 1, 5, 23, 99, 401, 1525, 6345, 27331, 122083, 520805, 2117293, 8301441, 34517395, 147850771, 628707981, 2675100397, 10920387779, 43701876543, 180872758207, 769658883325, 3243501133481, 13617178197183, 56148348498199 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 MATHEMATICA Table[Total[Abs[CoefficientList[Expand[(1+x-3x^2)^n], x]]], {n, 0, 30}] (* Harvey P. Dale, Mar 26 2013 *) PROG (PARI) for(n=0, 40, S=0; for(k=0, 2*n, t=polcoeff((1+x-3*x^2)^n, k, x); S=S+abs(t)); print1(S", ")) CROSSREFS Cf. A002426, A084600-A084614. Sequence in context: A323922 A119012 A215038 * A181331 A268400 A339232 Adjacent sequences:  A084612 A084613 A084614 * A084616 A084617 A084618 KEYWORD nonn AUTHOR Paul D. Hanna, Jun 01 2003 STATUS approved

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Last modified July 28 19:21 EDT 2021. Contains 346335 sequences. (Running on oeis4.)