OFFSET
1,1
COMMENTS
a(239) has 3137 decimal digits and is too long for inclusion in the b-file. - Alois P. Heinz, Aug 05 2024
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..238 (first 91 terms from N. J. A. Sloane)
MAPLE
b:= proc(n) option remember; (m->
`if`(isprime(m), ithprime(n)+1, 2*m-1))(b(n-1))
end: b(1):=2:
g:= proc(n) option remember; local k; for k from 1+g(n-1)
while not isprime(b(k)) do od; k
end: g(0):=0:
a:= n-> b(g(n)):
seq(a(n), n=1..38); # Alois P. Heinz, Aug 05 2024
MATHEMATICA
Reap[Module[{n = 1}, Nest[If[n++; PrimeQ[#], Sow[#]; Prime[n] + 1, 2*# - 1] &, 2, 500]]][[2, 1]] (* Paolo Xausa, Aug 07 2024 *)
PROG
(Python)
from itertools import count
from sympy import isprime, nextprime
def A373802_gen(): # generator of terms
a, p = 2, 3
for i in count(1):
if isprime(a):
yield a
a = p+1
else:
a = (a<<1)-1
p = nextprime(p)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Aug 05 2024
STATUS
approved