A164559 a(n) = 6^n/3 - 1.
1, 11, 71, 431, 2591, 15551, 93311, 559871, 3359231, 20155391, 120932351, 725594111, 4353564671, 26121388031, 156728328191, 940369969151, 5642219814911, 33853318889471, 203119913336831, 1218719480020991, 7312316880125951, 43873901280755711, 263243407684534271
Offset: 1
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..600
- Index entries for linear recurrences with constant coefficients, signature (7,-6).
Programs
-
Magma
[ 6^n/3-1: n in [1..20] ];
Formula
a(n) = 6*a(n-1)+5 for n > 2; a(1) = 1, a(2) = 11.
G.f.: x*(1+4*x)/((1-x)*(1-6*x)).