A157966 Number of 3's in A157733(n).

0, 1, 1, 1, 3, 3, 5, 5, 7, 9, 9, 11, 13, 13, 15, 17, 19, 19, 21, 23, 23, 25, 27, 29, 31, 33, 33, 35, 35, 37, 41, 43, 45, 45, 49, 49, 51, 53, 55, 57, 59, 59, 63, 63, 65, 65, 69, 73, 75, 75, 77, 79, 79, 83, 85, 87, 89, 89, 91, 93, 93, 97, 101, 103, 103, 105, 109, 111, 115, 115, 117

Offset: 0

Author

Paul Curtz, Mar 10 2009

Keywords

• nonn
• easy

Comments

Odd numbers missing in the sequence: 39, 47, 61, 67, 71, 81, 95, 99, 107, 113, 137, 141 etc.

The numbers above are essentially 2*A060461(n) - 1. - Mikhail Kurkov, Dec 18 2021

Crossrefs

Cf. A157733, A060461.

Programs

PARI

a(n) = if(n==2,1, (prime(n)-2)\3); \\ Kevin Ryde, Apr 25 2024

Formula

a(n) = floor((prime(n)-2)/3) for n != 2. - Kevin Ryde, Apr 25 2024

Extensions

Edited and extended by R. J. Mathar, Mar 15 2009