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

1,11

Comments

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

Links

Table of n, a(n) for n=1..13.

Antti Karttunen, PARI-program

Index entries for sequences related to primorial numbers

Formula

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

Prog

(PARI) \\ See the attached PARI-program.

Crossrefs

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

Sequence in context: A083707 A240651 A357432 * A346102 A346233 A358946

Adjacent sequences: A368997 A368998 A368999 * A369001 A369002 A369003

Keyword

nonn,hard,more

Author

Antti Karttunen, Jan 16 2024

Status

approved