A354791 Indices of nonprime terms in A354790.

1, 7, 14, 15, 17, 29, 31, 35, 59, 63, 64, 71, 79, 119, 120, 127, 129, 143, 159, 223, 239, 241, 255, 259, 260, 287, 288, 319, 320, 447, 479, 483, 484, 511, 512, 519, 521, 575, 577, 639, 641, 895, 959, 960, 967, 968, 969, 1023, 1025, 1039, 1043, 1044, 1151, 1152

Offset: 1

Author

Michael De Vlieger and N. J. A. Sloane, Jul 17 2022

Keywords

• nonn

Links

• Rémy Sigrist, Table of n, a(n) for n = 1..5715
• Rémy Sigrist, C program

Crossrefs

Cf. A354790, A354792.

Programs

C

See Links section.

Python

from math import lcm, gcd
from itertools import count, islice
from collections import deque
from sympy import factorint
def A354791_gen(): # generator of terms
    aset, aqueue, c, b, f, i = {1}, deque([1]), 2, 1, True, 1
    yield 1
    while True:
        for m in count(c):
            if m not in aset and gcd(m,b) == 1 and all(map(lambda n:n<=1,fs:=factorint(m).values())):
                i += 1
                if len(fs) > 1:
                    yield i
                aset.add(m)
                aqueue.append(m)
                if f: aqueue.popleft()
                b = lcm(*aqueue)
                f = not f
                while c in aset:
                    c += 1
                break
A354791_list = list(islice(A354791_gen(),30)) # Chai Wah Wu, Jul 17 2022

Extensions

More terms from Rémy Sigrist, Jul 17 2022