%I #9 Nov 10 2015 08:58:49
%S 2,4,6,2,10,12,2,16,18,2,22,4,2,28,30,2,2,36,2,40,42,2,46,6,2,52,2,2,
%T 58,60,2,4,66,2,70,72,2,2,78,2,82,4,2,88,6,2,2,96,2,100,102,2,106,108,
%U 2,112,2,2,2,10,2,4,126,2,130,6,2,136,138,2,2,4,2,148,150
%N Bisection of A258409: a(n) = A258409(2n+1).
%o (PARI) a(n) = gcd(apply(x->x-1, divisors(2*n+1)));
%Y Cf. A258409.
%K nonn
%O 1,1
%A _Michel Marcus_, Nov 10 2015