A127190 Expansion of e.g.f. sqrt((1+2*x)/(1+4*x)).

1, -1, 7, -75, 1089, -20025, 446535, -11715795, 353743425, -12084751665, 460905128775, -19414191656475, 895154327661825, -44844879530075625, 2425592881954016775, -140881250370301315875, 8745197742014671562625, -577792180264444615094625, 40483044280613870034474375

Offset

0,3

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Formula

E.g.f.: sqrt((1+2*x)/(1+4*x)).

D-finite with recurrence: a(n) +(6*n-5)*a(n-1) +8*(n-1)*(n-2)*a(n-2)=0. - R. J. Mathar, Jan 24 2020

Mathematica

With[{nn=20}, CoefficientList[Series[Sqrt[(1+2x)/(1+4x)], {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Apr 23 2014 *)

Crossrefs

Sequence in context: A365841 A243692 A258293 * A121316 A220215 A066302

Adjacent sequences: A127187 A127188 A127189 * A127191 A127192 A127193

Keyword

sign

Author

N. J. A. Sloane, Mar 26 2007

Status

approved