A354161 Index of A354160(n) in A090252.

15, 29, 47, 59, 63, 65, 121, 131, 193, 239, 241, 243, 255, 257, 265, 387, 479, 483, 487, 489, 515, 527, 529, 531, 767, 775, 777, 959, 961, 967, 969, 977, 979, 1023, 1031, 1055, 1059, 1063, 1143, 1551, 1553, 1555, 1921, 1923, 1935, 1937, 1939, 1951, 1953, 1955, 1959, 1961, 2047, 2063, 2064, 2111, 2113, 2119, 2127, 2288, 3071, 3073, 3105, 3107

Offset

1,1

Links

Michael De Vlieger, Table of n, a(n) for n = 1..2517

Prog

(Python)
from itertools import count, islice
from collections import deque
from math import gcd, lcm
from sympy import factorint
def A354161_gen(): # generator of terms
    aset, aqueue, c, b, f, i = {1}, deque([1]), 2, 1, True, 1
    while True:
        for m in count(c):
            if m not in aset and gcd(m, b) == 1:
                i += 1
                if len(fm := factorint(m)) == sum(fm.values()) == 2:
                    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
A354161_list = list(islice(A354161_gen(), 25)) # Chai Wah Wu, May 31 2022

Crossrefs

Cf. A090252, A354159, A354160, A354162, A354163.

Sequence in context: A001356 A104811 A131877 * A211324 A354163 A146427

Adjacent sequences: A354158 A354159 A354160 * A354162 A354163 A354164

Keyword

nonn

Author

N. J. A. Sloane, May 30 2022

Status

approved