A349994 a(n) is the difference between the n-th prime and the next smaller odd squarefree semiprime, divided by 2.

1, 2, 1, 4, 5, 1, 1, 2, 4, 1, 1, 2, 1, 1, 2, 1, 3, 1, 1, 3, 4, 6, 7, 1, 2, 1, 2, 3, 2, 3, 1, 1, 3, 6, 1, 2, 2, 3, 5, 6, 1, 1, 3, 4, 6, 1, 2, 1, 2, 2, 1, 2, 5, 7, 8, 1, 1, 1, 2, 4, 1, 1, 3, 4, 6, 2, 1, 1, 1, 1, 4, 1, 3, 1, 1, 2, 2, 3, 1, 3, 1, 2, 4, 5, 7, 3, 1, 1, 1

Offset

7,2

Links

Hugo Pfoertner, Table of n, a(n) for n = 7..10000

Example

a(7) = (17 - 15)/2 = 1,
a(8) = (19 - 15)/2 = 2,
a(9) = (23 - 21)/2 = 1,
a(10) = (29 - 21)/2 = 4.

Prog

(PARI) forprime(p=17, 500, forstep(k=p-2, 15, -2, if(omega(k)==2&&bigomega(k)==2, print1((p-k)/2, ", "); break)))

Crossrefs

Cf. A046388.

Sequence in context: A191660 A129874 A021983 * A194363 A161135 A237274

Adjacent sequences: A349991 A349992 A349993 * A349995 A349996 A349997

Keyword

nonn

Author

Hugo Pfoertner, Dec 12 2021

Status

approved