A117865 Number of palindromes (in base 6) below 6^n.

5, 10, 40, 70, 250, 430, 1510, 2590, 9070, 15550, 54430, 93310, 326590, 559870, 1959550, 3359230, 11757310, 20155390, 70543870, 120932350, 423263230, 725594110, 2539579390, 4353564670, 15237476350, 26121388030, 91424858110, 156728328190, 548549148670

Offset

1,1

Links

G. C. Greubel, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (1,6,-6).

Formula

a(n) = 7*6^((n-1)/2)-2 (n odd), 2*6^(n/2)-2 (n even).

G.f.: 5*x*(x+1) / ((x-1)*(6*x^2-1)). - Colin Barker, Feb 15 2013

Mathematica

Table[If[OddQ[n], 7*6^((n - 1)/2) - 2, 2*6^(n/2) - 2], {n, 25}] (* or *) LinearRecurrence[{1, 6, -6}, {5, 10, 40}, 25] (* G. C. Greubel, Oct 27 2016 *)

Crossrefs

Cf. A050250.

Sequence in context: A279764 A191580 A179306 * A249059 A163305 A001692

Adjacent sequences: A117862 A117863 A117864 * A117866 A117867 A117868

Keyword

nonn,base,easy

Author

Martin Renner, May 02 2006

Extensions

More terms from Colin Barker, Feb 15 2013

Status

approved