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A139596
A033587(n) followed by even hexagonal number A014635(n+1).
8
0, 6, 14, 28, 44, 66, 90, 120, 152, 190, 230, 276, 324, 378, 434, 496, 560, 630, 702, 780, 860, 946, 1034, 1128, 1224, 1326, 1430, 1540, 1652, 1770, 1890, 2016, 2144, 2278, 2414, 2556, 2700, 2850, 3002, 3160, 3320, 3486, 3654, 3828
OFFSET
0,2
COMMENTS
Sequence found by reading the line from 0, in the direction 0, 6,... and the same line from 0, in the direction 0, 14,..., in the square spiral whose vertices are the triangular numbers A000217.
FORMULA
Array read by rows: row n gives 8*n^2 + 6*n, 8*(n+1)^2 - 2(n+1).
O.g.f.: -2*x*(x+3)/((x-1)^3*(1+x)). - R. J. Mathar, May 06 2008
a(n) = 2*A156859(n). - R. J. Mathar, Feb 28 2018
EXAMPLE
Array begins:
0, 6
14, 28
44, 66
90, 120
MATHEMATICA
LinearRecurrence[{2, 0, -2, 1}, {0, 6, 14, 28}, 50] (* Harvey P. Dale, Jan 20 2024 *)
KEYWORD
easy,nonn
AUTHOR
Omar E. Pol, May 03 2008
STATUS
approved