A139615 a(n) = 105*n + 15.

15, 120, 225, 330, 435, 540, 645, 750, 855, 960, 1065, 1170, 1275, 1380, 1485, 1590, 1695, 1800, 1905, 2010, 2115, 2220, 2325, 2430, 2535, 2640, 2745, 2850, 2955, 3060, 3165, 3270, 3375, 3480, 3585, 3690, 3795, 3900, 4005, 4110, 4215

Offset

0,1

Comments

Numbers of the 15th column of positive numbers in the square array of nonnegative and polygonal numbers A139600. Also, numbers of the 15th column in the square array A057145.

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..5000

Index entries for linear recurrences with constant coefficients, signature (2,-1).

Formula

From Elmo R. Oliveira, Apr 04 2024: (Start)

G.f.: 15*(1+6*x)/(x-1)^2.

E.g.f.: 15*exp(x)*(1 + 7*x).

a(n) = 15*A016993(n).

a(n) = 2*a(n-1) - a(n-2) for n >= 2. (End)

Mathematica

105*Range[0, 40]+15 (* or *) LinearRecurrence[{2, -1}, {15, 120}, 50] (* Harvey P. Dale, May 07 2016 *)

Prog

(Magma) [15*(7*n + 1): n in [0..60]]; // Vincenzo Librandi, Jul 23 2011
(PARI) a(n)=105*n+15 \\ Charles R Greathouse IV, Oct 05 2011

Crossrefs

Cf. A016993, A057145, A139600.

Sequence in context: A162321 A161875 A259746 * A196506 A027484 A185542

Adjacent sequences: A139612 A139613 A139614 * A139616 A139617 A139618

Keyword

easy,nonn

Author

Omar E. Pol, Apr 27 2008

Status

approved