A376200 Indices where primes appear in A376198.

2, 3, 9, 10, 11, 23, 24, 25, 26, 52, 53, 54, 55, 56, 57, 58, 59, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 472, 473, 474, 475, 476, 477, 478, 479, 480, 481, 482, 483, 484, 485, 486, 487, 488

Offset

1,1

Comments

The primes appear in order, so a(n) is also the index of prime(n) in A376198.

Links

Michael S. Branicky, Table of n, a(n) for n = 1..100000

Prog

(Python)
from itertools import count, islice
from sympy import isprime, nextprime
def agen(): # generator of terms
    an, smc, smp = 2, 4, 3
    for n in count(2):
        if not isprime(an):
            an = smp if an == 2*smp else smc
        else:
            yield n
            an = smp if smp < smc else smc
        if an == smp: smp = nextprime(smp)
        else:
            smc += 1
            while isprime(smc): smc += 1
print(list(islice(agen(), 71))) # Michael S. Branicky, Oct 03 2024

Crossrefs

Cf. A376198, A376199, A376201, A376750-A376754.

Sequence in context: A270886 A133557 A047475 * A291610 A285428 A039012

Adjacent sequences: A376197 A376198 A376199 * A376201 A376202 A376203

Keyword

nonn

Author

N. J. A. Sloane, Oct 03 2024

Status

approved