cp's OEIS Frontend

A221218 Let sequence B_n={b_m} be defined by: b_1=prime(n), b_2=prime(n+1); for m>=3, b_m=b_(m-2)+b_(m-1) if b_(m-2)+b_(m-1) is not semiprime, otherwise b_m is the least prime divisor of b_(m-2)+b_(m-1). Then a(n) is the maximal term of sequence B_n, or a(n)=0 if B_n is unbounded.

%I A221218 #26 Nov 16 2014 06:47:06
%S A221218 570,570,570,570,19726,113750,570,22534,570,570,570,570,399610,570,
%T A221218 570,570,3138,670,570,570,772,570,570,2448,109472,570,570,570,1150,
%U A221218 609,18644,71049,2276,570,1634,1552,13844,798,68830,6940,575,1498,668,2551,1586,29729,1748,113750,19726,1435,194650,64360,3213,953988,9146,16539,811,8370238,516878,881,99942,7399,4160,215843,8397,676,13397,1715,915722,702,3572,141759,1192,1131,762,24895,1194,22534,1750,7069,68830
%N A221218 Let sequence B_n={b_m} be defined by: b_1=prime(n), b_2=prime(n+1); for m>=3, b_m=b_(m-2)+b_(m-1) if b_(m-2)+b_(m-1) is not semiprime, otherwise b_m is the least prime divisor of b_(m-2)+b_(m-1). Then a(n) is the maximal term of sequence B_n, or a(n)=0 if B_n is unbounded.
%C A221218 Conjecture: All a(n)>=570. Conjecture: All sequences B_n are eventually periodic.
%C A221218 Moreover, our first observations show that up to n=8, the lengths of the periods is 36.
%C A221218 _Peter J. C. Moses_ extended these observations and confirmed the same length 36 of all periods up to n=209.
%e A221218 In case n=1, B_1 essentially coincides with A214156 and thus a(1)=570 which is the maximal term of A214156.
%Y A221218 Cf. A214156.
%K A221218 nonn
%O A221218 1,1
%A A221218 _Vladimir Shevelev_, Feb 22 2013
%E A221218 Terms beginning with a(5) from _Peter J. C. Moses_