The On-Line Encyclopedia of Integer Sequences (OEIS)

A354160 revision #6

A354160

Products of exactly two distinct primes in A090252, in order of appearance.

21, 55, 26, 85, 57, 161, 319, 217, 481, 205, 731, 517, 159, 1121, 1403, 871, 355, 1241, 869, 2407, 1691, 413, 3007, 2323, 206, 1391, 4033, 565, 5207, 2227, 5891, 6533, 4321, 453, 1007, 623, 4867, 2231, 6161, 2119, 11189, 6401, 12709, 7421, 2159, 9563, 8213, 1507, 15247, 9259, 4031, 12367, 597, 2869, 11183, 1561, 13393, 7099, 3611, 14213, 478, 24823

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..62.

PROG

(Python)

from itertools import count, islice

from collections import deque

from math import gcd, lcm

from sympy import factorint

def A354160_gen(): # generator of terms

aset, aqueue, c, b, f = {1}, deque([1]), 2, 1, True

while True:

for m in count(c):

if m not in aset and gcd(m, b) == 1:

if len(fm := factorint(m)) == sum(fm.values()) == 2:

yield m

aset.add(m)

aqueue.append(m)

if f: aqueue.popleft()

b = lcm(*aqueue)

f = not f

while c in aset:

c += 1

break

A354160_list = list(islice(A354160_gen(), 25)) # Chai Wah Wu, May 31 2022

CROSSREFS

Cf. A090252, A354159, A354161, A354162, A354163.

Sequence in context: A304517 A007796 A211460 * A190664 A144302 A347373

Adjacent sequences: A354157 A354158 A354159 * A354161 A354162 A354163

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, May 30 2022

STATUS

proposed