A139267 Twice octagonal numbers: 2*n*(3*n-2).

0, 2, 16, 42, 80, 130, 192, 266, 352, 450, 560, 682, 816, 962, 1120, 1290, 1472, 1666, 1872, 2090, 2320, 2562, 2816, 3082, 3360, 3650, 3952, 4266, 4592, 4930, 5280, 5642, 6016, 6402, 6800, 7210, 7632, 8066, 8512, 8970, 9440, 9922

Offset

0,2

Comments

Sequence found by reading the line from 0, in the direction 0, 2,..., in the square spiral whose vertices are the generalized pentagonal numbers A001318. Opposite numbers to the members of A033580 in the same spiral. - Omar E. Pol, Sep 09 2011

After 0, a(n) = Sum_{i=0..n-1} (12*i + 2). - Bruno Berselli, Sep 11 2013

Links

G. C. Greubel, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

Formula

a(n) = 2*A000567(n) = 6*n^2 - 4*n = 2*n*(3*n - 2).

a(n) = a(n-1) + 12*n - 10, with n>0, a(0)=0. - Vincenzo Librandi, Aug 03 2010

G.f.: x*(2+10*x)/(1-3*x+3*x^2-x^3). - Colin Barker, Jan 06 2012

E.g.f.: 2*x*(1 + 3*x)*exp(x). - G. C. Greubel, Sep 18 2019

Maple

seq(2*n*(3*n-2), n=0..50); # G. C. Greubel, Sep 18 2019

Mathematica

Table[2*n*(3*n-2), {n, 0, 50}] (* G. C. Greubel, Jun 07 2017 *)

Prog

(PARI) a(n)=2*n*(3*n-2) \\ Charles R Greathouse IV, Oct 07 2015
(Magma) [2*n*(3*n-2): n in [0..50]]; // G. C. Greubel, Sep 18 2019
(Sage) [2*n*(3*n-2) for n in (0..50)] # G. C. Greubel, Sep 18 2019
(GAP) List([0..50], n-> 2*n*(3*n-2)); # G. C. Greubel, Sep 18 2019

Crossrefs

Cf. A000567, A017545.

Cf. numbers of the form n*(n*k-k+4))/2 listed in A226488 (this sequence is the case k=12).

Sequence in context: A034507 A211620 A023638 * A254855 A181340 A275032

Adjacent sequences: A139264 A139265 A139266 * A139268 A139269 A139270

Keyword

nonn,easy

Author

Omar E. Pol, May 14 2008, May 19 2008

Status

approved