A095894 a(2n) = 6*n^2 + 7*n + 1; a(2n+1) = 6*n^2 + 13*n + 7.

1, 7, 14, 26, 39, 57, 76, 100, 125, 155, 186, 222, 259, 301, 344, 392, 441, 495, 550, 610, 671, 737, 804, 876, 949, 1027, 1106, 1190, 1275, 1365, 1456, 1552, 1649, 1751, 1854, 1962, 2071, 2185, 2300, 2420, 2541, 2667, 2794, 2926, 3059, 3197, 3336, 3480

Offset: 0

Author

Gary W. Adamson, Jun 11 2004

Keywords

• nonn
• easy

Comments

From Omar E. Pol, Jul 18 2012: (Start)

Positive terms of A051866 and positive terms of A049453 interleaved.

Also sequence found by reading the line from 1, in the direction 1, 14, ..., and the line from 7, in the direction 7, 26, ..., in the square spiral whose vertices are the generalized pentagonal numbers A001318. (End)

Links

• G. C. Greubel, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (2,0,-2,1).

Crossrefs

Cf. A047225 (first differences), A049453, A051866.

Programs

Mathematica

LinearRecurrence[{2,0,-2,1},{1,7,14,26},60] (* Harvey P. Dale, Oct 13 2016 *)

PARI

x='x+O('x^50); Vec((-1-5*x)/((1+x)*(x-1)^3)) \\ G. C. Greubel, Jun 19 2017

Formula

G.f.: ( -1-5*x ) / ( (1+x)*(x-1)^3 ). - R. J. Mathar, Oct 26 2011

Extensions

Edited by Don Reble, Nov 16 2005