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).

7, 23, 131, 47, 643, 2459, 2000807, 503347241, 82125909539251, 9617692012399, 55555555342491359799151, 1116817987709786226917069, 578610396154837, 66992050984853, 254497141, 1660738053545999, 201525986561, 25600818891233, 796725607788661087, 23547857117470471

Offset

0,1

Links

Tyler Busby, Table of n, a(n) for n = 0..22

Mathematica

NestWhileList[FactorInteger[2+#*Prime[PrimePi[ # ]-2]][[ -1, 1]] &, 7, True, 8] (* T. D. Noe, Nov 15 2006 *)
NestList[FactorInteger[NextPrime[NextPrime[#, -1], -1]#+2][[-1, 1]]&, 7, 20] (* Harvey P. Dale, Dec 26 2017 *)

Crossrefs

Cf. A082032, A031441, A031442.

Sequence in context: A064640 A064639 A064638 * A227254 A080082 A158954

Adjacent sequences: A082018 A082019 A082020 * A082022 A082023 A082024

Keyword

nonn

Author

Yasutoshi Kohmoto, May 10 2003

Extensions

Description corrected by Rick L. Shepherd, Dec 19 2004

Corrected by T. D. Noe, Nov 15 2006

More terms from Harvey P. Dale, Dec 26 2017

a(19) from Tyler Busby, Oct 12 2023

Status

approved