A242211 - OEIS

%I #28 Sep 13 2022 13:04:58

%S 4,6,12,36,144,1296,20736,1679616,429981696

%N a(1) = 4, a(n) = A222208(a(n-1)).

%C The definition "a(1) = 2, a(n) = A222208(a(n-1))" produces the periodic sequence 2, 3, 2, 3, 2, 3, 2, ... .

%C From _Lechoslaw Ratajczak_, May 23 2022: (Start)

%C It appears that a(n) = 2^(2^floor((n-1)/2))*3^(2^floor((n-2)/2)) (for n > 1). If it is true, a(10) = 2821109907456.

%C The definition "b(1) = 8, b(k) = A222208(b(k-1))" produces the sequence: 8, 18, 48, 324, 2304, 104976, ... . It appears that b(k) = 2^A135530(k-1)*3^A135530(k-2) (for k > 1). (End)

%e a(3) = 12 because a(2) = 6 and A222208(6) = 12.

%Y Cf. A222208, A222209.

%K nonn,more

%O 1,1

%A _J. Lowell_, May 07 2014

%E a(8) from _Alois P. Heinz_, May 07 2014

%E a(9) from _Sean A. Irvine_, Jul 18 2022