A113471 - OEIS

A113471

Lucas(k)/(3k) for k = 2*3^n, where Lucas(k) is k-th Lucas number (A000032).

1, 107, 1190741689, 14769352340699478579719327005523, 253650450218391594062880777243777017638488805917392303113120204411172926964476779033181303378188721

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OFFSET

1,2

COMMENTS

a(n) divides a(n+1). a(n+1)/a(n) = {107, 11128427, 12403489755282666163307, 17174107866559209832245996776509546318861182768126017871860347845227, ...}. a(n+1)/a(n) is prime for n = {1, 2, 4}.

LINKS

Table of n, a(n) for n=1..5.

FORMULA

a(n) = ( Fibonacci[ 2*3^n - 1 ] + Fibonacci[ 2*3^n + 1 ] ) / ( 2*3^(n+1) ). a(n) = A000032[ 2*3^n ] / ( 2*3^(n+1) ).

MATHEMATICA

Table[ ( Fibonacci[ 2*3^n - 1 ] + Fibonacci[ 2*3^n + 1 ] ) / ( 2*3^(n+1) ), {n, 1, 5} ]

CROSSREFS

Cf. A000032, A016089 = numbers n such that n divides n-th Lucas number. Cf. A128935 = Fibonacci(5^n) / 5^n.

Sequence in context: A160488 A158476 A145045 * A057388 A192071 A025601

Adjacent sequences: A113468 A113469 A113470 * A113472 A113473 A113474

KEYWORD

nonn

AUTHOR

Alexander Adamchuk, May 13 2007

STATUS

approved