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A194713
13 times hexagonal numbers: 13*n*(2*n-1).
1
0, 13, 78, 195, 364, 585, 858, 1183, 1560, 1989, 2470, 3003, 3588, 4225, 4914, 5655, 6448, 7293, 8190, 9139, 10140, 11193, 12298, 13455, 14664, 15925, 17238, 18603, 20020, 21489, 23010, 24583, 26208, 27885, 29614, 31395, 33228, 35113, 37050, 39039
OFFSET
0,2
COMMENTS
Sequence found by reading the line from 0, in the direction 0, 13, ..., in the square spiral whose vertices are the generalized 15-gonal numbers.
FORMULA
a(n) = 26*n^2 - 13*n = 13*A000384(n).
a(n) = a(n-1) + 52*n - 39, a(0)=0. - Vincenzo Librandi, Oct 03 2011
PROG
(Magma) [13*n*(2*n-1): n in [0..50]]; // Vincenzo Librandi, Oct 03 2011
(PARI) a(n)=13*n*(2*n-1) \\ Charles R Greathouse IV, Jun 17 2017
KEYWORD
nonn,easy
AUTHOR
Omar E. Pol, Oct 02 2011
STATUS
approved