OFFSET
1,2
COMMENTS
Except a(1), the same as A054888. - R. J. Mathar, Nov 28 2011
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..2392
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 (3,-1).
FORMULA
a(n) = 3*a(n-1) - a(n-2), n>2.
G.f.: 5*x^2 / (x^2 - 3*x + 1). - Colin Barker, Apr 08 2013
a(n) = 5*Fibonacci(2*n-2) = Lucas(2*n-1) + Lucas(2*n-3) with Lucas(-1) = -1. - Bruno Berselli, Feb 15 2017
a(n) = Lucas(n)^2 - Lucas(n-2)^2. - Greg Dresden, Apr 15 2022
EXAMPLE
15 is in the sequence because 15^2 = 5*7^2 - 20.
MATHEMATICA
LinearRecurrence[{3, -1}, {0, 5}, 50]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Sture Sjöstedt, Nov 27 2011
EXTENSIONS
More terms from Colin Barker, Apr 08 2013
STATUS
approved