A020901 Greatest k such that k-th prime < 3 times n-th prime.

3, 4, 6, 8, 11, 12, 15, 16, 19, 23, 24, 29, 30, 31, 34, 37, 40, 42, 46, 47, 47, 51, 53, 56, 61, 62, 63, 66, 66, 68, 75, 77, 80, 80, 86, 87, 91, 93, 95, 97, 99, 100, 105, 106, 107, 108, 115, 121, 123, 124, 125, 127, 128, 133, 136, 138, 139, 141, 145

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Mathematica

Table[PrimePi[NextPrime[3Prime[n], -1]], {n, 60}] (* Harvey P. Dale, Feb 21 2014 *)

Prog

(PARI) a(n) = primepi(3*prime(n)) \\ Michel Marcus, Mar 22 2013

Crossrefs

Cf. A020900, A020934-A020940.

Sequence in context: A080728 A047414 A109402 * A181714 A371594 A057057

Adjacent sequences: A020898 A020899 A020900 * A020902 A020903 A020904

Keyword

nonn

Author

Clark Kimberling

Status

approved