A065101 a(0) = c, a(1) = p*c^3; a(n+2) = p*c^2*a(n+1) - a(n), for p = 3, c = 2.

2, 24, 286, 3408, 40610, 483912, 5766334, 68712096, 818778818, 9756633720, 116260825822, 1385373276144, 16508218487906, 196713248578728, 2344050764456830, 27931895924903232, 332838700334381954

Offset

0,1

Links

Harry J. Smith, Table of n, a(n) for n = 0..100

J.-P. Ehrmann et al., Problem POLYA002, Integer pairs (x,y) for which (x^2+y^2)/(1+pxy) is an integer.

Tanya Khovanova, Recursive Sequences

Index entries for linear recurrences with constant coefficients, signature (12,-1).

Formula

G.f.: 2/(1 - 12*x + x^2). - Floor van Lamoen, Feb 07 2002

a(n) = 2*A004191(n). - R. J. Mathar, Sep 27 2014

Mathematica

a[0] = c; a[1] = p*c^3; a[n_] := a[n] = p*c^2*a[n - 1] - a[n - 2]; p = 3; c = 2; Table[ a[n], {n, 0, 20} ]

Prog

(PARI): polya002(3, 2, 18). For definition of function polya002 see A052530.
(PARI) { p=3; c=2; k=p*c^2; for (n=0, 100, if (n>1, a=k*a1 - a2; a2=a1; a1=a, if (n, a=a1=k*c, a=a2=c)); write("b065101.txt", n, " ", a) ) } \\ Harry J. Smith, Oct 07 2009

Crossrefs

Cf. A052530.

Sequence in context: A002006 A230129 A355951 * A052739 A135389 A336310

Adjacent sequences: A065098 A065099 A065100 * A065102 A065103 A065104

Keyword

easy,nonn

Author

N. J. A. Sloane, Nov 12 2001

Status

approved