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A158551 a(n) = 26*n^2 - 1. 2
25, 103, 233, 415, 649, 935, 1273, 1663, 2105, 2599, 3145, 3743, 4393, 5095, 5849, 6655, 7513, 8423, 9385, 10399, 11465, 12583, 13753, 14975, 16249, 17575, 18953, 20383, 21865, 23399, 24985, 26623, 28313, 30055, 31849, 33695, 35593, 37543 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The identity (26*n^2 - 1)^2 - (169*n^2 - 13)*(2*n)^2 = 1 can be written as a(n)^2 - A158550(n)*A005843(n)^2 = 1.

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

FORMULA

G.f.: x*(-25 - 28*x + x^2)/(x-1)^3.

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).

MATHEMATICA

LinearRecurrence[{3, -3, 1}, {25, 103, 233}, 40] (* Vincenzo Librandi, Feb 14 2012 *)

PROG

(MAGMA) I:=[25, 103, 233]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+Self(n-3): n in [1..50]]; // Vincenzo Librandi, Feb 14 2012

(PARI) for(n=1, 40, print1(26*n^2-1", ")); \\ Vincenzo Librandi, Feb 14 2012

CROSSREFS

Cf. A005843, A158550.

Sequence in context: A042220 A114254 A042222 * A044276 A044657 A160437

Adjacent sequences:  A158548 A158549 A158550 * A158552 A158553 A158554

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Mar 21 2009

EXTENSIONS

Comment rewritten by R. J. Mathar, Oct 16 2009

STATUS

approved

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Last modified August 19 06:22 EDT 2022. Contains 356216 sequences. (Running on oeis4.)