A013712 a(n) = 7^(2*n + 1).

7, 343, 16807, 823543, 40353607, 1977326743, 96889010407, 4747561509943, 232630513987207, 11398895185373143, 558545864083284007, 27368747340080916343, 1341068619663964900807, 65712362363534280139543, 3219905755813179726837607, 157775382034845806615042743

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..150
• Tanya Khovanova, Recursive Sequences
• Index entries for linear recurrences with constant coefficients, signature (49).

Crossrefs

Cf. A000420, A005408, A087752.

Programs

Magma

[7^(2*n+1): n in [0..20]]; // Vincenzo Librandi, May 26 2011

Mathematica

NestList[49#&,7,20] (* Harvey P. Dale, Jul 15 2019 *)

PARI

a(n)=7^(2*n+1) \\ Charles R Greathouse IV, Jul 11 2016

Formula

From Philippe Deléham, Nov 24 2008: (Start)

a(n) = 49*a(n-1); a(0)=7.

G.f.: 7/(1-49*x).

a(n) = 7*A087752(n). (End)

From Elmo R. Oliveira, Aug 27 2024: (Start)

E.g.f.: 7*exp(49*x).

a(n) = A000420(A005408(n)). (End)