login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A157436 128n^2 + 2528n + 12481. 3
15137, 18049, 21217, 24641, 28321, 32257, 36449, 40897, 45601, 50561, 55777, 61249, 66977, 72961, 79201, 85697, 92449, 99457, 106721, 114241, 122017, 130049, 138337, 146881, 155681, 164737, 174049, 183617, 193441, 203521, 213857, 224449 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The identity (128*n^2+2528*n+12481)^2-(4*n^2+79*n+390)*(64*n+632)^2=1 can be written as a(n)^2-A157434(n)* A157435(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 (3,-3,1).

FORMULA

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

G.f.: x*(-12481*x^2-27362*x-15137)/(x-1)^3.

MATHEMATICA

LinearRecurrence[{3, -3, 1}, {15137, 18049, 21217}, 50]

PROG

(MAGMA) I:=[15137, 18049, 21217]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..50]];

(PARI) a(n) = 128*n^2 + 2528*n + 12481.

CROSSREFS

Cf. A157434, A157435.

Sequence in context: A004935 A004955 A004975 * A196495 A031623 A105924

Adjacent sequences:  A157433 A157434 A157435 * A157437 A157438 A157439

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Mar 01 2009

EXTENSIONS

Corrected by Charles R Greathouse IV, Jul 29 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 April 21 22:12 EDT 2019. Contains 322328 sequences. (Running on oeis4.)