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!)
 A157660 a(n) = 8000*n - 40. 3
 7960, 15960, 23960, 31960, 39960, 47960, 55960, 63960, 71960, 79960, 87960, 95960, 103960, 111960, 119960, 127960, 135960, 143960, 151960, 159960, 167960, 175960, 183960, 191960, 199960, 207960, 215960, 223960, 231960, 239960, 247960, 255960 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The identity (80000*n^2 - 800*n + 1)^2 - (100*n^2 - n)*(8000*n - 40)^2 = 1 can be written as A157661(n)^2 - A157659(n)*a(n)^2 = 1 (see also the second part of the comment at A157661). - Vincenzo Librandi, Jan 28 2012 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). - Vincenzo Librandi, Jan 28 2012 G.f.: x*(40*x+7960)/(x-1)^2. - Vincenzo Librandi, Jan 28 2012 E.g.f.: 40*(1 - (1 - 200*x)*exp(x)). G. C. Greubel, Nov 17 2018 MATHEMATICA LinearRecurrence[{2, -1}, {7960, 15960}, 40] (* Vincenzo Librandi, Jan 28 2012 *) PROG (Magma) I:=[7960, 15960]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]]; // Vincenzo Librandi, Jan 28 2012 (PARI) for(n=1, 40, print1(8000*n-40", ")); \\ Vincenzo Librandi, Jan 28 2012 (Sage) [40*(200*n - 1) for n in (1..40)] # G. C. Greubel, Nov 17 2018 (GAP) List([1..40], n -> 40*(200*n - 1)); # G. C. Greubel, Nov 17 2018 CROSSREFS Cf. A157659, A157661. Sequence in context: A293623 A316908 A254138 * A236786 A252190 A233730 Adjacent sequences: A157657 A157658 A157659 * A157661 A157662 A157663 KEYWORD nonn,easy AUTHOR Vincenzo Librandi, Mar 04 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 11:54 EST 2022. Contains 358521 sequences. (Running on oeis4.)