OFFSET
1,1
COMMENTS
The identity (242*n + 1)^2 - (121*n^2 + n)*22^2 = 1 can be written as A157958(n)^2 - a(n)*22^2 = 1. - Vincenzo Librandi, Feb 06 2012
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Vincenzo Librandi, X^2-AY^2=1
E. J. Barbeau, Polynomial Excursions, Chapter 10: Diophantine equations (2010), pages 84-85 (row 14 in the first table at p. 85, case d(t) = t*(11^2*t+1)).
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
G.f.: x*(-122 - 120*x)/(x-1)^3. - Vincenzo Librandi, Feb 06 2012
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - Vincenzo Librandi, Feb 06 2012
MATHEMATICA
LinearRecurrence[{3, -3, 1}, {122, 486, 1092}, 50] (* Vincenzo Librandi, Feb 06 2012 *)
Table[121n^2+n, {n, 50}] (* Harvey P. Dale, Dec 15 2019 *)
PROG
(Magma)[121*n^2+n: n in [1..50]];
(PARI) for(n=1, 50, print1(121*n^2 + n", ")); \\ Vincenzo Librandi, Feb 06 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 22 2010
STATUS
approved