A198763 a(n) = 4*5^n-1.

3, 19, 99, 499, 2499, 12499, 62499, 312499, 1562499, 7812499, 39062499, 195312499, 976562499, 4882812499, 24414062499, 122070312499, 610351562499, 3051757812499, 15258789062499, 76293945312499, 381469726562499, 1907348632812499

Offset: 0

Author

Vincenzo Librandi, Oct 30 2011

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (6,-5).

Crossrefs

Cf. A024049, A057651, A081655.

Programs

Magma

[4*5^n-1: n in [0..30]]

Mathematica

CoefficientList[Series[(3 + x)/(1 - 6*x + 5*x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Jan 04 2013 *)
NestList[5#+4&,3,30] (* or *) LinearRecurrence[{6,-5},{3,19},30] (* Harvey P. Dale, Jul 03 2021 *)

Formula

a(n) = 5*a(n-1)+4.

a(n) = 6*a(n-1)-5*a(n-2), n>1.

G.f.: (3 + x)/(1 - 6*x + 5*x^2). - Vincenzo Librandi, Jan 04 2013