A117861 Number of palindromes of length n (in base 9).
8, 8, 72, 72, 648, 648, 5832, 5832, 52488, 52488, 472392, 472392, 4251528, 4251528, 38263752, 38263752, 344373768, 344373768, 3099363912, 3099363912, 27894275208, 27894275208, 251048476872, 251048476872, 2259436291848, 2259436291848, 20334926626632
Offset: 1
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
- Index entries for linear recurrences with constant coefficients, signature (0,9).
Programs
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Mathematica
Table[8 9^Floor[(n-1)/2],{n,50}] (* Harvey P. Dale, Oct 21 2011 *)
Formula
a(n) = 8*9^floor((n-1)/2).
G.f.: 8*x*(1+x)/(1-9*x^2). a(n) = 8*3^(n-2)*(2-(-1)^n). - Bruno Berselli, Oct 24 2011
Extensions
More terms from Harvey P. Dale, Oct 21 2011