A355606 The indices where A354606(n) = 1.

1, 2, 4, 9, 14, 25, 37, 57, 99, 133, 182, 191, 404, 469, 595, 640, 780, 1195, 1884, 2407, 2808, 3010, 3217, 3444, 4245, 4383, 5773, 8703, 10069, 10731, 12640, 14470, 17998, 18535, 22648, 23341, 24286, 27431, 33702, 37019, 45593, 53759, 56598, 57578, 76640, 96729, 99557, 106881, 125900, 144162

Offset: 1

Author

Scott R. Shannon, Jul 09 2022

Keywords

• nonn

Comments

See A354606 for further details.

Crossrefs

Cf. A354606, A000005.

Programs

Mathematica

c[] := 0; j = 1; nn = 2^20; {1}~Join~Reap[Monitor[Do[k = ++c[DivisorSigma[0, j]]; If[k == 1, Sow[n]]; j = k, {n, 2, nn}], n] ][[-1, 1]] (* _Michael De Vlieger, Dec 12 2024 *)

Python

from sympy import divisor_count
from collections import Counter
from itertools import count, islice
def f(n): return divisor_count(n)
def agen():
    n, an, fan, inventory = 1, 1, 1, Counter([1])
    yield n
    for n in count(2):
        an = inventory[fan]
        fan = f(an)
        inventory.update([fan])
        if an == 1: yield n
print(list(islice(agen(), 50))) # Michael S. Branicky, Jul 09 2022