A158230 a(n) = 256*n^2 + 2*n.
258, 1028, 2310, 4104, 6410, 9228, 12558, 16400, 20754, 25620, 30998, 36888, 43290, 50204, 57630, 65568, 74018, 82980, 92454, 102440, 112938, 123948, 135470, 147504, 160050, 173108, 186678, 200760, 215354, 230460, 246078, 262208, 278850, 296004
Offset: 1
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 15 in the first table at p. 85, case d(t) = t*(16^2*t+2)).
- Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
Crossrefs
Cf. A158231.
Programs
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Magma
I:=[258, 1028, 2310]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..50]];
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Mathematica
LinearRecurrence[{3,-3,1},{258,1028,2310},50] -
PARI
a(n) = 256*n^2+2*n
Formula
a(n) = 3*a(n-1) -3*a(n-2) +a(n-3).
G.f.: 2*x*(129+127*x)/(1-x)^3.
E.g.f.: 2*exp(x)*x*(129 + 128*x). - Stefano Spezia, Aug 19 2025
Comments