A013894 a(n) = 20^(5*n + 1).

20, 64000000, 204800000000000, 655360000000000000000, 2097152000000000000000000000, 6710886400000000000000000000000000, 21474836480000000000000000000000000000000, 68719476736000000000000000000000000000000000000, 219902325555200000000000000000000000000000000000000000

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..50
• Tanya Khovanova, Recursive Sequences.
• Index entries for linear recurrences with constant coefficients, signature (3200000).

Crossrefs

Subsequence of A009964.

Cf. A013822, A013854, A016861.

Programs

Magma

[20^(5*n+1): n in [0..10]]; // Vincenzo Librandi, May 27 2011

Mathematica

NestList[3200000*# &, 20, 10] (* Paolo Xausa, Jul 13 2025 *)

Formula

a(n) = 3200000*a(n-1), a(0)=20. - Vincenzo Librandi, May 27 2011

From Elmo R. Oliveira, Jul 11 2025: (Start)

G.f.: 20/(1-3200000*x).

E.g.f.: 20*exp(3200000*x).

a(n) = A013822(n)*A013854(n) = A009964(A016861(n)). (End)