OFFSET
0,2
COMMENTS
Number of domino tilings of a 2 X (2n-1) projective plane.
Numbers m such that 3*m^2+16 is a square. [Bruno Berselli, Dec 16 2014]
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
W. K. Alt, Enumeration of Domino Tilings on the Projective Grid Graph, A Thesis Presented to The Division of Mathematics and Natural Sciences, Reed College, May 2013.
Hacène Belbachir, Soumeya Merwa Tebtoub, and László Németh, Ellipse Chains and Associated Sequences, J. Int. Seq., Vol. 23 (2020), Article 20.8.5.
Index entries for linear recurrences with constant coefficients, signature (4,-1).
FORMULA
G.f.: 4*x/(1-4*x+x^2). - Philippe Deléham, Nov 19 2013
a(n) = ((2*(-(2-sqrt(3))^n+(2+sqrt(3))^n)))/sqrt(3). - Colin Barker, Oct 12 2015
MATHEMATICA
LinearRecurrence[{4, -1}, {0, 4}, 30] (* Harvey P. Dale, Oct 01 2015 *)
PROG
(PARI) concat(0, Vec(4*x/(1-4*x+x^2) + O(x^40))) \\ Colin Barker, Oct 12 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Nov 18 2013
EXTENSIONS
More terms and other edits by M. F. Hasler, Nov 20 2013
STATUS
approved