

A195316


Centered 36gonal numbers.


7



1, 37, 109, 217, 361, 541, 757, 1009, 1297, 1621, 1981, 2377, 2809, 3277, 3781, 4321, 4897, 5509, 6157, 6841, 7561, 8317, 9109, 9937, 10801, 11701, 12637, 13609, 14617, 15661, 16741, 17857, 19009, 20197, 21421, 22681, 23977, 25309, 26677, 28081, 29521
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OFFSET

1,2


COMMENTS

Sequence found by reading the line from 1, in the direction 1, 37, ..., in the square spiral whose vertices are the generalized hendecagonal numbers A195160. Semiaxis opposite to A195321 in the same spiral.


LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Index entries for linear recurrences with constant coefficients, signature (3,3,1).


FORMULA

a(n) = 18*n^2  18*n + 1.
G.f.: x*(1 + 34*x + x^2) / (x1)^3.  R. J. Mathar, Sep 18 2011


PROG

(MAGMA) [(18*n^218*n+1): n in [1..50]]; // Vincenzo Librandi, Sep 19 2011
(PARI) a(n)=18*n^218*n+1 \\ Charles R Greathouse IV, Oct 07 2015


CROSSREFS

Bisection of A195147.
Cf. A003154, A069129, A069133, A069190, A195314, A195315, A195317, A195318.
Sequence in context: A171833 A257117 A033215 * A176549 A118536 A003164
Adjacent sequences: A195313 A195314 A195315 * A195317 A195318 A195319


KEYWORD

nonn,easy


AUTHOR

Omar E. Pol, Sep 16 2011


STATUS

approved



