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Index of A354160(n) in A090252.
4

%I #11 Jun 15 2022 16:47:29

%S 15,29,47,59,63,65,121,131,193,239,241,243,255,257,265,387,479,483,

%T 487,489,515,527,529,531,767,775,777,959,961,967,969,977,979,1023,

%U 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

%N Index of A354160(n) in A090252.

%H Michael De Vlieger, <a href="/A354161/b354161.txt">Table of n, a(n) for n = 1..2517</a>

%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 A354161_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 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 A354161_list = list(islice(A354161_gen(),25)) # _Chai Wah Wu_, May 31 2022

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

%K nonn

%O 1,1

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