A157627 8000n - 6040.

1960, 9960, 17960, 25960, 33960, 41960, 49960, 57960, 65960, 73960, 81960, 89960, 97960, 105960, 113960, 121960, 129960, 137960, 145960, 153960, 161960, 169960, 177960, 185960, 193960, 201960, 209960, 217960, 225960, 233960, 241960, 249960

Offset

1,1

Comments

The identity (80000*n^2-120800*n+45601)^2-(100*n^2-151*n +57)*(8000*n-6040)^2=1 can be written as A157628(n)^2-A157626(n)*a(n)^2=1.

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

Vincenzo Librandi, X^2-AY^2=1

Index entries for linear recurrences with constant coefficients, signature (2,-1).

Formula

a(n) = 2*a(n-1) - a(n-2).

G.f.: x*(1960+6040*x)/(x-1)^2.

Mathematica

LinearRecurrence[{2, -1}, {1960, 9960}, 40]

Prog

(Magma) I:=[1960, 9960]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..40]];
(PARI) a(n)=8000*n-6040 \\ Charles R Greathouse IV, Dec 27 2011

Crossrefs

Cf. A157626, A157628.

Sequence in context: A209946 A200857 A351680 * A072598 A159213 A056094

Adjacent sequences: A157624 A157625 A157626 * A157628 A157629 A157630

Keyword

nonn,easy

Author

Vincenzo Librandi, Mar 03 2009

Status

approved