A351907 Number of prime quadruples p < q < r < prime(n) in arithmetic progression.

0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 2, 0, 0, 0, 0, 1, 1, 0, 2, 1, 1, 1, 0, 1, 1, 3, 0, 1, 1, 1, 2, 1, 2, 1, 0, 1, 2, 1, 2, 1, 0, 3, 3, 1, 2, 1, 1, 1, 3, 1, 1, 1, 0, 2, 4, 3, 1, 1, 1, 2, 2, 0, 2, 1, 4, 2, 2, 1, 0, 2, 4, 2, 3, 1, 2, 3, 2, 3, 2, 3, 3, 2, 1, 4, 3, 2, 2, 2, 0, 1, 4, 1, 1

Offset

1,17

Links

Table of n, a(n) for n=1..99.

Example

a(9) = 1 corresponds to the quadruple (5, 11, 17, 23) where 23 is the 9th prime.

Prog

(PARI) a(n, q=prime(n))=my(s); forprimestep(p=q%6, q-18, 6, isprime((2*p+q)/3) && isprime((2*q+p)/3) && s++); s

Crossrefs

Cf. A351908 (partial sums).

Sequence in context: A174875 A193510 A353337 * A357374 A264048 A101257

Adjacent sequences: A351904 A351905 A351906 * A351908 A351909 A351910

Keyword

nonn

Author

Charles R Greathouse IV, Feb 25 2022

Status

approved