A376199 Index where n appears in A376198.

1, 2, 3, 4, 9, 5, 10, 6, 7, 8, 11, 12, 23, 13, 14, 15, 24, 16, 25, 17, 18, 19, 26, 20, 21, 22, 27, 28, 52, 29, 53, 30, 31, 32, 33, 34, 54, 35, 36, 37, 55, 38, 56, 39, 40, 41, 57, 42, 43, 44, 45, 46, 58, 47, 48, 49, 50, 51, 59, 60, 110, 61, 62, 63, 64, 65, 111, 66, 67, 68, 112, 69, 113, 70, 71, 72, 73, 74, 114, 75, 76, 77, 115, 78, 79

Offset: 1

Author

N. J. A. Sloane, Oct 03 2024

Keywords

• nonn

Links

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

Crossrefs

Cf. A376198, A376200-A376201, A376750-A376754.

Programs

Python

from itertools import count, islice
from sympy import isprime, nextprime
def agen(): # generator of terms
    an, smc, smp, adict, n = 2, 4, 3, {1: 1, 2: 2}, 1
    for k in count(3):
        if not isprime(an):
            an = smp if an == 2*smp else smc
        else:
            an = smp if smp < smc else smc
        if an == smp: smp = nextprime(smp)
        else:
            smc += 1
            while isprime(smc): smc += 1
        if an not in adict: adict[an] = k
        while n in adict: yield adict[n]; n += 1
print(list(islice(agen(), 85))) # Michael S. Branicky, Oct 03 2024