A036544 a(n) = (2*(1 + n + (((10^n-1)/9) - n)/9)).

2, 4, 8, 32, 256, 2480, 24704, 246928, 2469152, 24691376, 246913600, 2469135824, 24691358048, 246913580272, 2469135802496, 24691358024720, 246913580246944

Offset: 0

Author

Antti Karttunen

Keywords

• nonn
• easy

Comments

Result of applying extrapolator to terms 3-7 of A000301.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000
• A. Karttunen, Lisp Source (see function g and sequence cddr_of_mult2last)
• Index entries for linear recurrences with constant coefficients, signature (12, -21, 10).

Programs

Magma

[(2*(1+n+(((10^n-1)/9)-n)/9)): n in [0..30]]; // Vincenzo Librandi, Nov 11 2011

Mathematica

LinearRecurrence[{12,-21,10},{2,4,8},20] (* Harvey P. Dale, Mar 11 2025 *)

Formula

a(n) = (2/81)*(72*n + 10^n + 80).

G.f.: 2*(1 - 10*x + x^2)/((1-10*x)*(1-x)^2). - Bruno Berselli, Nov 11 2011