%I A082021
%S A082021 7,23,131,47,643,2459,2000807,503347241
%N A082021 a(0) = 7; for n > 0, a(n) is the greatest prime factor of PP(PP(a(n-1)))*a(n-1)+2 
               where PP(n) is an abbreviation for PreviousPrime(n).
%t A082021 NestWhileList[FactorInteger[2+#*Prime[PrimePi[ # ]-2]][[ -1,1]] &, 7, 
               True, 8] - T. D. Noe (noe(AT)sspectra.com), Nov 15 2006
%Y A082021 Cf. A082032, A031441, A031442.
%Y A082021 Sequence in context: A064640 A064639 A064638 this_sequence A080082 A158954 
               A056205
%Y A082021 Adjacent sequences: A082018 A082019 A082020 this_sequence A082022 A082023 
               A082024
%K A082021 nonn
%O A082021 0,1
%A A082021 Yasutoshi Kohmoto (zbi74583(AT)boat.zero.ad.jp), May 10 2003
%E A082021 Description corrected by Rick L. Shepherd (rshepherd2(AT)hotmail.com), 
               Dec 19 2004
%E A082021 Corrected by T. D. Noe (noe(AT)sspectra.com), Nov 15 2006