A356764
Semiprimes divisible by their indices in the sequence of semiprimes, divided by those indices.
Original entry on oeis.org
4, 3, 3, 3, 3, 3, 3, 5, 5, 5, 5, 5, 5, 7, 7, 7, 7
Offset: 1
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With[{sp=Select[Range[5*10^6],PrimeOmega[#]==2&]},Select[#[[1]]/#[[2]]&/@Thread[{sp,Range[Length[sp]]}],IntegerQ]] (* The program generates the first 13 terms of the sequence. *) (* Harvey P. Dale, Aug 07 2025 *)
A357741
Semiprimes k such that k is divisible by its index in the sequence of semiprimes.
Original entry on oeis.org
4, 6, 9, 21, 33, 129, 159, 3066835, 3067195, 3067255, 3067615, 3067745, 3068045, 44690978227, 44690978647, 44690978983, 44690979529
Offset: 1
The 1st semiprime is 4, which is divisible by 1, so 4 is in the sequence.
The 4th semiprime is 10, which is not divisible by 4, so 10 is not in the sequence.
The 7th semiprime is 21, which is divisible by 7, so 21 is in the sequence.
Showing 1-2 of 2 results.
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