

A195320


7 times hexagonal numbers: 7*n*(2*n1).


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
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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 semidiagonals 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) / (x1)^3.  R. J. Mathar, Sep 27 2011


PROG

(Magma) [7*n*(2*n1): n in [0..50]]; // Vincenzo Librandi, Sep 28 2011
(PARI) a(n)=7*n*(2*n1) \\ 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



