A369000 a(n) is the number of integers, not semiprimes, whose arithmetic derivative is equal to the n-th primorial.

0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 2, 9, 18

Offset: 1

Author

Antti Karttunen, Jan 16 2024

Keywords

• nonn
• hard
• more

Comments

a(n) = number of solutions k to equation A003415(k) = A002110(n) with A001222(k) > 2.

Links

• Antti Karttunen, PARI-program
• Index entries for sequences related to primorial numbers

Crossrefs

Cf. A001222, A002110, A003415, A116979, A351029, A366890 (solutions themselves).

Programs

PARI

\\ See the attached PARI-program.

Formula

a(n) = A351029(n) - A116979(n).