A104298 a(n) = prime((a(n-1) + 1)/2), a(1) = 15.

15, 19, 29, 47, 89, 197, 523, 1667, 6397, 29437, 160423, 1023227, 7552957, 63845779, 612095179, 6597973097, 79345496843, 1057111639847, 15505433597669, 248978989034081, 4354591985875057, 82572975649180463, 1690509511954186499

Offset

1,1

Comments

All the terms are primes except a(1) which is an odd integer.

Sequences with other values of a(1): A104296 and A104297.

Links

Table of n, a(n) for n=1..23.

Mathematica

a[1] = 15; a[n_] := a[n] = Prime[(a[n - 1] + 1)/2]; Table[ a[n], {n, 19}] (* Robert G. Wilson v, Mar 24 2005 *)
NestList[Prime[(#+1)/2]&, 15, 18] (* Harvey P. Dale, Aug 04 2018 *)

Crossrefs

Cf. A104296, A104297, A116457.

Sequence in context: A234849 A164564 A211329 * A032475 A169728 A167054

Adjacent sequences: A104295 A104296 A104297 * A104299 A104300 A104301

Keyword

nonn,more

Author

Zak Seidov, Feb 28 2005

Extensions

a(14)-a(19) from Robert G. Wilson v, Mar 24 2005

a(20)-a(23) from Amiram Eldar, Jul 15 2025

Status

approved