A041760 Numerators of continued fraction convergents to sqrt(401).

20, 801, 32060, 1283201, 51360100, 2055687201, 82278848140, 3293209612801, 131810663360180, 5275719744020001, 211160600424160220, 8451699736710428801, 338279150068841312260, 13539617702490362919201, 541922987249683358080300

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• cofr
• frac
• easy
• less

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..200
• Tanya Khovanova, Recursive Sequences
• Index entries for linear recurrences with constant coefficients, signature (40,1).

Crossrefs

Cf. A041761, A040380.

Programs

Mathematica

Numerator[Convergents[Sqrt[401], 30]] (* Vincenzo Librandi, Nov 07 2013 *)

Formula

a(n) = 40*a(n-1)+a(n-2) for n>1, a(0)=20, a(1)=801. G.f.: (20+x)/(1-40*x-x^2). [Philippe Deléham, Nov 23 2008]