This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A001504 a(n) = (3n+1)(3n+2). 4
 2, 20, 56, 110, 182, 272, 380, 506, 650, 812, 992, 1190, 1406, 1640, 1892, 2162, 2450, 2756, 3080, 3422, 3782, 4160, 4556, 4970, 5402, 5852, 6320, 6806, 7310, 7832, 8372, 8930, 9506, 10100, 10712, 11342, 11990, 12656, 13340, 14042, 14762, 15500, 16256, 17030 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS The oblong numbers (A002378) not divisible by 3. - Gionata Neri, May 10 2015 LINKS T. D. Noe, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA Sum_{k>=0} 1/a(k) = (Pi/3)/sqrt(3). - Benoit Cloitre, Aug 20 2002 a(n) = 18*n + a(n-1) with a(0) = 2. - Vincenzo Librandi, Nov 12 2010 MAPLE A001504:=n->(3*n+1)*(3*n+2): seq(A001504(n), n=0..100); # Wesley Ivan Hurt, Jan 29 2017 MATHEMATICA Table[(3*n+1)*(3*n+2), {n, 50}] (* Vladimir Joseph Stephan Orlovsky, Jan 22 2012 *) PROG (PARI) a(n)=(3*n+1)*(3*n+2) \\ Charles R Greathouse IV, Jun 17 2017 CROSSREFS Cf. a(n) = A060544(n+1)*2. Subsequence of A002378. Sequence in context: A059211 A139271 A133217 * A192351 A136905 A230644 Adjacent sequences:  A001501 A001502 A001503 * A001505 A001506 A001507 KEYWORD nonn,easy AUTHOR 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.

Last modified December 7 03:00 EST 2019. Contains 329836 sequences. (Running on oeis4.)