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

1,2

Links

Table of n, a(n) for n=1..61.

Prog

(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

Crossrefs

Cf. A352187, A352192.

Sequence in context: A030763 A143145 A328212 * A256393 A130664 A014011

Adjacent sequences: A352188 A352189 A352190 * A352192 A352193 A352194

Keyword

nonn

Author

N. J. A. Sloane, Mar 13 2022

Status

approved