This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A082021 #20 Dec 17 2024 18:25:42 %S A082021 7,23,131,47,643,2459,2000807,503347241,82125909539251,9617692012399, %T A082021 55555555342491359799151,1116817987709786226917069,578610396154837, %U A082021 66992050984853,254497141,1660738053545999,201525986561,25600818891233,796725607788661087,23547857117470471 %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). %H A082021 Tyler Busby, <a href="/A082021/b082021.txt">Table of n, a(n) for n = 0..25</a> %t A082021 NestWhileList[FactorInteger[2+#*Prime[PrimePi[ # ]-2]][[ -1,1]] &, 7, True, 8] (* _T. D. Noe_, Nov 15 2006 *) %t A082021 NestList[FactorInteger[NextPrime[NextPrime[#,-1],-1]#+2][[-1,1]]&,7,20] (* _Harvey P. Dale_, Dec 26 2017 *) %Y A082021 Cf. A082032, A031441, A031442. %K A082021 nonn %O A082021 0,1 %A A082021 _Yasutoshi Kohmoto_, May 10 2003 %E A082021 Description corrected by _Rick L. Shepherd_, Dec 19 2004 %E A082021 Corrected by _T. D. Noe_, Nov 15 2006 %E A082021 More terms from _Harvey P. Dale_, Dec 26 2017 %E A082021 a(19) from _Tyler Busby_, Oct 12 2023