A354163 - OEIS

%I #9 Jun 01 2022 02:01:30

%S 15,29,59,63,65,121,131,193,239,241,243,255,257,265,387,479,483,487,

%T 489,515,527,529,531,775,777,959,961,967,969,977,979,1023,1031,1055,

%U 1059,1063,1143,1551,1553,1555,1921,1923,1935,1937,1939,1951,1953,1955,1959,1961,2047,2063,2064,2111,2113,2119,2127,2288,3073,3105,3107,3111,3113,3839

%N Index of A354162(n) in A090252.

%o (Python)

%o from itertools import count, islice

%o from collections import deque

%o from math import gcd, lcm

%o from sympy import factorint

%o def A354163_gen(): # generator of terms

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

%o     while True:

%o         for m in count(c):

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

%o                 i += 1

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

%o                     yield i

%o                 aset.add(m)

%o                 aqueue.append(m)

%o                 if f: aqueue.popleft()

%o                 b = lcm(*aqueue)

%o                 f = not f

%o                 while c in aset:

%o                     c += 1

%o                 break

%o A354163_list = list(islice(A354163_gen(),25)) # _Chai Wah Wu_, May 31 2022

%Y Cf. A090252, A354159, A354160, A354161, A354162.

%K nonn

%O 1,1

%A _N. J. A. Sloane_, May 30 2022