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 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 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 PROG (PARI) a(n)=10*n^2-7*n+1 \\ Charles R Greathouse IV, Jun 17 2017 CROSSREFS Sequence in context: A175701 A227866 A180576 * A272858 A272818 A272859 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

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Last modified June 17 07:31 EDT 2019. Contains 324183 sequences. (Running on oeis4.)