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A117859
Number of palindromes of length n (in base 7).
0
6, 6, 42, 42, 294, 294, 2058, 2058, 14406, 14406, 100842, 100842, 705894, 705894, 4941258, 4941258, 34588806, 34588806, 242121642, 242121642, 1694851494, 1694851494, 11863960458, 11863960458, 83047723206, 83047723206, 581334062442, 581334062442
OFFSET
1,1
FORMULA
a(n) = 6*7^floor((n-1)/2).
a(n) = 7*a(n-2). G.f.: 6*x*(1+x)/(1-7*x^2). [Colin Barker, Jun 30 2012]
MATHEMATICA
6*7^Floor[Range[0, 40]/2] (* Harvey P. Dale, Mar 23 2012 *)
CROSSREFS
Cf. A050683.
Sequence in context: A278734 A279535 A125510 * A229159 A102901 A014435
KEYWORD
nonn,base,easy
AUTHOR
Martin Renner, May 02 2006
EXTENSIONS
More terms from Harvey P. Dale, Mar 23 2012
STATUS
approved