A356764 Semiprimes divisible by their indices in the sequence of semiprimes, divided by those indices.

4, 3, 3, 3, 3, 3, 3, 5, 5, 5, 5, 5, 5, 7, 7, 7, 7

Offset

1,1

Comments

Except for a(1) = 4, all terms are prime.

Links

Table of n, a(n) for n=1..17.

Lucas A. Brown, semiprimemods.py

Formula

a(n) = A357741(n) / A106125(n).

Mathematica

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 *)

Crossrefs

Cf. A001358, A106125, A357741.

Sequence in context: A143487 A031350 A031353 * A085415 A187470 A374419

Adjacent sequences: A356761 A356762 A356763 * A356765 A356766 A356767

Keyword

nonn,hard,more

Author

Lucas A. Brown, Oct 13 2022

Status

approved