The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A158316 400n^2 - 2n. 2
 398, 1596, 3594, 6392, 9990, 14388, 19586, 25584, 32382, 39980, 48378, 57576, 67574, 78372, 89970, 102368, 115566, 129564, 144362, 159960, 176358, 193556, 211554, 230352, 249950, 270348, 291546, 313544, 336342, 359940, 384338, 409536 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The identity (400*n-1)^2-(400*n^2-2*n)*(20)^2=1 can be written as A158317(n)^2-a(n)*(20)^2=1. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..10000 Vincenzo Librandi, X^2-AY^2=1 E. J. Barbeau, Polynomial Excursions, Chapter 10: Diophantine equations (2010), pages 84-85 (row 15 in the first table at p. 85, case d(t) = t*(20^2*t-2)). 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*(-398-402*x)/(x-1)^3. MATHEMATICA LinearRecurrence[{3, -3, 1}, {398, 1596, 3594}, 50] PROG (Magma) I:=[398, 1596, 3594]; [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) = 400*n^2 - 2*n. CROSSREFS Cf. A158317. Sequence in context: A327592 A340419 A191942 * A236713 A235958 A187515 Adjacent sequences: A158313 A158314 A158315 * A158317 A158318 A158319 KEYWORD nonn,easy AUTHOR Vincenzo Librandi, Mar 16 2009 STATUS approved

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

Last modified December 3 11:24 EST 2022. Contains 358517 sequences. (Running on oeis4.)