A109909 a(n) = number of primes of the form k*(n-k)-1.

0, 0, 0, 2, 2, 1, 2, 1, 4, 1, 3, 2, 3, 2, 3, 2, 4, 3, 5, 1, 10, 1, 5, 5, 4, 2, 6, 3, 5, 3, 9, 4, 11, 3, 5, 5, 5, 5, 14, 1, 6, 6, 7, 6, 11, 5, 8, 4, 15, 3, 13, 4, 10, 9, 6, 5, 11, 4, 12, 5, 13, 4, 12, 4, 6, 11, 13, 4, 12, 6, 15, 12, 9, 4, 9, 5, 10, 8, 10, 3, 28, 7, 11, 15, 6, 9, 20, 7, 20, 6, 17, 5, 23

Offset

1,4

Comments

Conjecture: a(n) > 0 for n > 3.

Conjecture verified up to 10^9. - Mauro Fiorentini, Jul 23 2023

Links

Table of n, a(n) for n=1..93.

Pengcheng Niu and Junli Zhang, On Two Conjectures of A. Murthy, ResearchGate (2024).

Crossrefs

Cf. A109904, A109905, A026728, A109907, A109908.

Sequence in context: A262403 A343491 A326952 * A254573 A144387 A030768

Adjacent sequences: A109906 A109907 A109908 * A109910 A109911 A109912

Keyword

nonn

Author

Amarnath Murthy, Jul 15 2005

Extensions

More terms from David Wasserman, Aug 15 2005

Status

approved