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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A158186 a(n) = 10*n^2 - 7*n + 1. 3
 1, 4, 27, 70, 133, 216, 319, 442, 585, 748, 931, 1134, 1357, 1600, 1863, 2146, 2449, 2772, 3115, 3478, 3861, 4264, 4687, 5130, 5593, 6076, 6579, 7102, 7645, 8208, 8791, 9394, 10017, 10660, 11323, 12006, 12709, 13432, 14175, 14938, 15721, 16524, 17347 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Sequence found by reading the segment (1, 4) together with the line (one of the diagonal axes) from 4, in the direction 4, 27, ..., in the square spiral whose vertices are the generalized heptagonal numbers A085787. - Omar E. Pol, Sep 10 2011 LINKS Table of n, a(n) for n=0..42. Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA a(n) = (2*n-1)*(5*n-1). a(n) = A033571(n) - A008596(n) = A010010(n) - A033571(n). G.f.: (1+x+18*x^2)/(1-x)^3. - Jaume Oliver Lafont, Mar 27 2009 a(n) = a(n-1) + 20*n - 17 (with a(0)=1). - Vincenzo Librandi, Dec 03 2010 Sum_{n>=0} 1/a(n) = 1 + (2*sqrt(1+2/sqrt(5))*Pi - 2*sqrt(5)*log(phi) - 5*log(5) + 8*log(2))/12, where phi is the golden ratio (A001622). - Amiram Eldar, Sep 22 2022 MATHEMATICA Table[10n^2-7n+1, {n, 0, 50}] (* or *) LinearRecurrence[{3, -3, 1}, {1, 4, 27}, 50] (* Harvey P. Dale, Apr 06 2020 *) PROG (PARI) a(n)=10*n^2-7*n+1 \\ Charles R Greathouse IV, Jun 17 2017 CROSSREFS Cf. A001622, A008596, A010010, A033571, A085787. Sequence in context: A227866 A356814 A180576 * A272858 A272818 A356433 Adjacent sequences: A158183 A158184 A158185 * A158187 A158188 A158189 KEYWORD nonn,easy AUTHOR Reinhard Zumkeller, Mar 13 2009 EXTENSIONS Typo in definition corrected by Reinhard Zumkeller, Dec 03 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 September 13 05:16 EDT 2024. Contains 375859 sequences. (Running on oeis4.)