A338937 - OEIS

%I #9 Nov 16 2020 23:33:17

%S 1,2,2,4,6,9,11,17,28,28,22,24,22,22,26,28,26,26,30,25,20,19,28,30,21,

%T 20,19,28,30,21,20,19,28,30,21,20,19,28,30,21,20,19,28,30,21,20,19,28,

%U 30,21,20,19,28,30,21,20,19,28,30,21,20,19,28,30,21,20,19,28,30,21,20,19,28,30,21,20,19

%N a(n+1) = A001414(a(n)) + A001414(a(n-1)) with a(0)=1, a(1)=2.

%C Enters 5-cycle 20,19,28,30,21 starting with a(20).

%F a(n) = a(n-5) for n >= 25.

%F a(n+1) = A001414(a(n)*a(n-1)).

%e a(5) = A001414(6) + A001414(4) = 5 + 4 = 9.

%p spf:= n -> add(t[1]*t[2],t=ifactors(n)[2]):

%p N:= 100:

%p A:= Array(0..N): A[0]:= 1: A[1]:= 2:

%p for n from 2 to N do

%p   A[n]:= spf(A[n-1])+spf(A[n-2])

%p od:

%p seq(A[i],i=0..N);

%Y Cf. A001414, A338938.

%K nonn

%O 0,2

%A _J. M. Bergot_ and _Robert Israel_, Nov 16 2020