A117982 Trisection of A117981.

1, 7, 73, 511, 3577, 37303, 262657, 1838599, 19173961, 134217727, 939524089, 9797894071, 68585258497, 480096809479, 5006723870281, 35253225520639, 246772578644473, 2573485463006647, 18014398643699713, 126100790505897991

Offset

0,2

Comments

Divisors of a(9)=2^(3^3)-1=2^27-1 are a(0),a(1),a(2),a(3),a(6),a(7),a(8),a(9). Divisors of a(3)=2^(3^2)-1=2^9-1 are a(0),a(1),a(2),a(3).

Links

Table of n, a(n) for n=0..19.

Formula

a(n)=sum{k=0..3n, (-1)^(3n-k)*L(C(3n,k)/3)*2^k} where L(j/p) is the Legendre symbol of j and p.

Crossrefs

Sequence in context: A202042 A294291 A318688 * A003535 A050917 A308418

Adjacent sequences: A117979 A117980 A117981 * A117983 A117984 A117985

Keyword

easy,nonn

Author

Paul Barry, Apr 06 2006

Status

approved