A073124 a(n) = prime(1+prime(n)) - prime(prime(n)).

2, 2, 2, 2, 6, 2, 2, 4, 6, 4, 4, 6, 2, 2, 12, 10, 4, 10, 6, 6, 6, 8, 2, 2, 12, 10, 6, 6, 2, 2, 10, 4, 14, 12, 4, 4, 10, 4, 6, 2, 6, 4, 10, 10, 12, 6, 4, 14, 6, 4, 10, 12, 8, 4, 6, 24, 10, 6, 2, 8, 14, 18, 2, 6, 2, 12, 16, 4, 6, 6, 2, 6, 26, 2, 8, 10, 4, 10, 4

Offset

1,1

Comments

Number of entries in {x,..} such that PrimePi[x]=Prime[n].

Links

Table of n, a(n) for n=1..79.

Formula

a(n) = Card{x; A000720(x) = A000040(n)}.

a(n) = A072677(n) - A006450(n).

Example

n = 25: p(25) = 97, Pi[x] = 97 holds for 12 numbers: X = {509, 510, 511, 512, 513, 514, 515, 516, 517, 518, 519, 520} so a(25) = 12. Largest 520 = A073123(25), smallest = A006450(25).

Mathematica

Table[Prime[Prime[n]+1]-Prime[Prime[n]], {n, 1, 256}]

Prog

(PARI) a(n) =  prime(1+prime(n)) - prime(prime(n)); \\ Michel Marcus, Dec 11 2013

Crossrefs

Cf. A000720, A000040, A006450, A072677, A073123.

Sequence in context: A114005 A103794 A273258 * A278260 A070877 A156717

Adjacent sequences: A073121 A073122 A073123 * A073125 A073126 A073127

Keyword

nonn

Author

Labos Elemer, Jul 16 2002

Extensions

More terms from Michel Marcus, Dec 11 2013

Status

approved