A305629 Number of values of k, 0 < k < n, for which (2*n^2 + 2*k*n - k^2 - k)/2 is prime.

0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 0, 3, 3, 1, 3, 5, 2, 2, 4, 2, 1, 4, 3, 2, 4, 1, 4, 4, 2, 4, 4, 3, 1, 3, 2, 4, 12, 3, 2, 7, 1, 7, 15, 3, 4, 6, 3, 8, 8, 2, 4, 10, 6, 7, 7, 3, 6, 16, 3, 4, 6, 3, 8, 7, 4, 5, 11, 5, 4, 7, 5, 8, 12, 2, 12, 8, 4, 16, 9, 3, 8, 24, 6, 8, 11, 5, 8, 19, 3

Offset

0,9

Comments

It appears that a(A046174(n)) = 0.

Links

Table of n, a(n) for n=0..90.

Prog

(PARI) a(n) = sum(k=1, n-1, isprime((2*n^2+2*k*n-k^2-k)/2))

Crossrefs

Cf. A046174.

Sequence in context: A341894 A171932 A358094 * A214664 A214666 A320471

Adjacent sequences: A305626 A305627 A305628 * A305630 A305631 A305632

Keyword

nonn

Author

Gionata Neri, Jul 08 2018

Status

approved