A352191 Records in A352187.

1, 2, 4, 6, 9, 12, 15, 18, 21, 24, 25, 30, 33, 36, 39, 42, 51, 56, 57, 77, 121, 207, 333, 345, 371, 391, 469, 871, 1111, 1121, 1341, 1557, 1719, 2043, 2051, 2367, 3421, 3951, 4527, 6127, 6849, 10307, 11007, 11061, 11079, 11133, 11511, 14113, 16753, 16839, 16911, 17973, 18153, 19161, 27731, 28831, 29447, 36949, 46783, 49093, 49577

Offset: 1

Author

N. J. A. Sloane, Mar 13 2022

Keywords

• nonn

Crossrefs

Cf. A352187, A352192.

Programs

Python

from math import gcd
from itertools import count, islice
from sympy import primefactors
def A352191_gen(): # generator of terms
    bset, blist, mmax, c = {1,2}, [1,2], 3, 2
    yield from blist
    while True:
        for m in count(mmax):
            if gcd(m,blist[-1]) > 1 and m not in bset:
                if all(blist[-2] % p == 0 for p in primefactors(blist[-1])) or gcd(m,blist[-2]) == 1:
                    if m > c:
                        yield m
                        c = m
                    blist = [blist[-1],m]
                    bset.add(m)
                    while mmax in bset:
                        mmax += 1
                    break
A352191_list = list(islice(A352191_gen(),30)) # Chai Wah Wu, Mar 14 2022