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 A194431 a(n) = 8*n^2 - 6*n - 1. 5
 1, 19, 53, 103, 169, 251, 349, 463, 593, 739, 901, 1079, 1273, 1483, 1709, 1951, 2209, 2483, 2773, 3079, 3401, 3739, 4093, 4463, 4849, 5251, 5669, 6103, 6553, 7019, 7501, 7999, 8513, 9043, 9589, 10151, 10729, 11323, 11933, 12559, 13201, 13859, 14533 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Sequence found by reading the line from 1, in the direction 1, 19, ..., in the square spiral whose vertices are the triangular numbers A000217. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..10000 Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA G.f.: x*(-1 - 16*x + x^2) / (x-1)^3. - R. J. Mathar, Sep 06 2011 PROG (MAGMA) [8*n^2 - 6*n - 1: n in [1..50]]; Vincenzo Librandi, Sep 07 2011 (PARI) a(n)=8*n^2-6*n-1 \\ Charles R Greathouse IV, Oct 07 2015 CROSSREFS Cf. A014634, A051870, A069129, A139098, A194268. Sequence in context: A118591 A031341 A165982 * A024848 A240136 A072581 Adjacent sequences:  A194428 A194429 A194430 * A194432 A194433 A194434 KEYWORD nonn,easy AUTHOR Omar E. Pol, Sep 05 2011 STATUS approved

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Last modified April 11 18:00 EDT 2021. Contains 342888 sequences. (Running on oeis4.)