A121201 a(n) = 7^n+5^n-2n.

2, 10, 70, 462, 3018, 19922, 133262, 901654, 6155410, 42306714, 292240854, 2026154846, 14085427802, 98109713506, 684326588446, 4778079088038, 33385518460194, 233393453440298, 1632228295176038, 11417968671701230

Offset: 0

Author

Mohammad K. Azarian, Aug 19 2006

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (14,-60,82,-35).

Crossrefs

Cf. A074616.

Programs

Magma

[7^n+5^n-2*n: n in [0..20]]; // Vincenzo Librandi, Feb 25 2013

Magma

I:=[2,10,70,462]; [n le 4 select I[n] else 14*Self(n-1)-60*Self(n-2)+82*Self(n-3)-35*Self(n-4): n in [1..20]]; // Vincenzo Librandi, Feb 25 2013

Mathematica

CoefficientList[Series[2 (1 - 9 x + 25 x^2 - 41 x^3)/((1-x)^2 (1-5 x)(1-7 x)), {x, 0, 30}], x] (* Vincenzo Librandi, Feb 25 2013 *)
LinearRecurrence[{14,-60,82,-35},{2,10,70,462},30] (* Harvey P. Dale, Dec 21 2014 *)

Formula

G.f.: 2*(1-9*x+25*x^2-41*x^3)/((1-x)^2*(1-5*x)*(1-7*x)). - Vincenzo Librandi, Feb 25 2013

a(n) = 14*a(n-1)-60*a(n-2)+82*a(n-3)-35*a(n-4). - Vincenzo Librandi, Feb 26 2013

Extensions

Edited by Ray Chandler, Sep 06 2006