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 A195320 7 times hexagonal numbers: 7*n*(2*n-1). 12
 0, 7, 42, 105, 196, 315, 462, 637, 840, 1071, 1330, 1617, 1932, 2275, 2646, 3045, 3472, 3927, 4410, 4921, 5460, 6027, 6622, 7245, 7896, 8575, 9282, 10017, 10780, 11571, 12390, 13237, 14112, 15015, 15946, 16905, 17892, 18907, 19950, 21021, 22120, 23247, 24402 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Sequence found by reading the line from 0, in the direction 0, 7, ..., in the square spiral whose vertices are the generalized enneagonal numbers A118277. Also sequence found by reading the same line (mentioned above) in the Pythagorean spiral whose edges have length A195019 and whose vertices are the numbers A195020. This is the one of the semi-diagonals of the square spiral, which is related to the primitive Pythagorean triple [3, 4, 5]. - Omar E. Pol, Oct 13 2011 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..10000 Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA a(n) = 14*n^2 - 7*n = 7*A000384(n). G.f.: -7*x*(1+3*x) / (x-1)^3. - R. J. Mathar, Sep 27 2011 PROG (Magma) [7*n*(2*n-1): n in [0..50]]; // Vincenzo Librandi, Sep 28 2011 (PARI) a(n)=7*n*(2*n-1) \\ Charles R Greathouse IV, Sep 28 2015 CROSSREFS Bisection of A024966. Cf. A000384, A118277, A152746, A152750, A185019, A193053, A198017. Sequence in context: A102532 A297405 A044109 * A110451 A212144 A266387 Adjacent sequences: A195317 A195318 A195319 * A195321 A195322 A195323 KEYWORD nonn,easy AUTHOR Omar E. Pol, Sep 18 2011 STATUS approved

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Last modified November 28 00:05 EST 2022. Contains 358406 sequences. (Running on oeis4.)