OFFSET
1,2
COMMENTS
Also, numbers m such that 9*m+4 is a square. After 0, therefore, there are no squares in this sequence. - Bruno Berselli, Jan 07 2016
LINKS
Bruno Berselli, Table of n, a(n) for n = 1..1000
S. Cooper and M. D. Hirschhorn, Results of Hurwitz type for three squares. Discrete Math. 274 (2004), no. 1-3, 9-24. See B(q).
Index entries for linear recurrences with constant coefficients, signature (1,2,-2,-1,1).
FORMULA
From Bruno Berselli, Feb 04 2012: (Start)
G.f.: x*(5+8*x+5*x^2)/((x+1)^2*(1-x)^3).
MATHEMATICA
CoefficientList[Series[x*(5+8*x+5*x^2)/((x+1)^2*(1-x)^3), {x, 0, 50}], x] (* G. C. Greubel, Jun 20 2017 *)
LinearRecurrence[{1, 2, -2, -1, 1}, {0, 5, 13, 28, 44}, 50] (* Harvey P. Dale, Jan 23 2018 *)
PROG
(Magma) [0] cat &cat[[9*n^2-4*n, 9*n^2+4*n]: n in [1..32]]; // Bruno Berselli, Feb 04 2011
(PARI) x='x+O('x^50); Vec(x*(5+8*x+5*x^2)/((x+1)^2*(1-x)^3)) \\ G. C. Greubel, Jun 20 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Feb 04 2012
STATUS
approved