login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A156639 a(n) = 169*n^2 - 140*n + 29. 4
58, 425, 1130, 2173, 3554, 5273, 7330, 9725, 12458, 15529, 18938, 22685, 26770, 31193, 35954, 41053, 46490, 52265, 58378, 64829, 71618, 78745, 86210, 94013, 102154, 110633, 119450, 128605, 138098, 147929, 158098 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The identity (57122*n^2 - 47320*n + 9801)^2 - (169*n^2 - 140*n + 29)*(4394*n - 1820)^2 = 1 can be written as A156721(n)^2 - a(n)*A156627(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*(58 + 251*x + 29*x^2)/(1 - x)^3.

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

MATHEMATICA

LinearRecurrence[{3, -3, 1}, {58, 425, 1130}, 40]

PROG

(MAGMA) I:=[58, 425, 1130]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+Self(n-3): n in [1..40]];

(PARI) a(n)=169*n^2-140*n+29 \\ Charles R Greathouse IV, Dec 23 2011

CROSSREFS

Cf. A156627, A156721.

Sequence in context: A235443 A235511 A255684 * A249003 A249468 A232378

Adjacent sequences:  A156636 A156637 A156638 * A156640 A156641 A156642

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Feb 15 2009

EXTENSIONS

Edited by Charles R Greathouse IV, Jul 25 2010

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 30 19:33 EDT 2021. Contains 346359 sequences. (Running on oeis4.)