login
A095894
a(2n) = 6*n^2 + 7*n + 1; a(2n+1) = 6*n^2 + 13*n + 7.
2
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
0,2
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)
FORMULA
G.f.: ( -1-5*x ) / ( (1+x)*(x-1)^3 ). - R. J. Mathar, Oct 26 2011
MATHEMATICA
LinearRecurrence[{2, 0, -2, 1}, {1, 7, 14, 26}, 60] (* Harvey P. Dale, Oct 13 2016 *)
PROG
(PARI) x='x+O('x^50); Vec((-1-5*x)/((1+x)*(x-1)^3)) \\ G. C. Greubel, Jun 19 2017
CROSSREFS
Cf. A047225 (first differences), A049453, A051866.
Sequence in context: A232871 A232854 A232790 * A104599 A115874 A083495
KEYWORD
nonn,easy
AUTHOR
Gary W. Adamson, Jun 11 2004
EXTENSIONS
Edited by Don Reble, Nov 16 2005
STATUS
approved