A238111 Twice the large Schroeder numbers A006318.

2, 4, 12, 44, 180, 788, 3612, 17116, 83172, 412196, 2075436, 10586892, 54595476, 284157492, 1490774076, 7875206076, 41854313412, 223636052036, 1200637707852, 6473448634348, 35037238641780, 190299310403924, 1036863750837852, 5665846701859484, 31042935297750180, 170499885177942628

Offset

0,1

Comments

Although this is simply twice A006318, it seems to arise often enough to warrant its own entry. See also A001003.

Links

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

Li Guo and Jun Pei, Averaging algebras, Schroeder numbers and rooted trees, arXiv preprint arXiv:1401.7386, 2014

Formula

G.f.: (1-x-sqrt(x^2-6*x+1))/x.

Mathematica

Table[-2 I Sqrt[2] LegendreP[n, -1, 2, 3], {n, 0, 25}] (* Jean-François Alcover, Feb 15 2019 *)

Crossrefs

Cf. A006318, A001003.

Sequence in context: A346505 A180205 A131529 * A165901 A074449 A364622

Adjacent sequences: A238108 A238109 A238110 * A238112 A238113 A238114

Keyword

nonn

Author

N. J. A. Sloane, Mar 04 2014

Status

approved