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A373803
Indices of primes in A373801.
3
1, 3, 6, 10, 19, 23, 25, 29, 31, 33, 36, 45, 48, 60, 91, 95, 101, 105, 108, 112, 116, 121, 124, 129, 142, 149, 155, 157, 161, 163, 173, 176, 185, 227, 229, 231, 238, 240, 386, 391, 393, 398, 411, 415, 435, 439, 466, 537, 543, 565, 570, 575, 577, 588, 592, 687, 694, 696, 700, 733, 738, 759
OFFSET
1,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..442 (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:
a:= proc(n) option remember; local k; for k from 1+a(n-1)
while not isprime(b(k)) do od; k
end: a(0):=0:
seq(a(n), n=1..62); # Alois P. Heinz, Aug 05 2024
MATHEMATICA
Reap[Module[{n = 1}, Nest[If[n++; PrimeQ[#], Sow[n-1]; Prime[n] + 1, 2*# - 1] &, 2, 1000]]][[2, 1]] (* Paolo Xausa, Aug 07 2024 *)
PROG
(Python)
from itertools import count
from sympy import isprime, nextprime
def A373803_gen(): # generator of terms
a, p = 2, 3
for i in count(1):
if isprime(a):
yield i
a = p+1
else:
a = (a<<1)-1
p = nextprime(p)
A373803_list = list(islice(A373803_gen(), 20)) # Chai Wah Wu, Aug 05 2024
CROSSREFS
Sequence in context: A080014 A364403 A360892 * A132274 A253768 A091714
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Aug 05 2024
STATUS
approved