A085341 Number of primes between sigma(n) and n inclusive.

0, 1, 0, 2, 0, 2, 0, 2, 2, 3, 0, 4, 0, 3, 3, 5, 0, 5, 0, 5, 3, 3, 0, 8, 2, 4, 3, 7, 0, 10, 0, 7, 4, 5, 4, 13, 0, 5, 4, 12, 0, 11, 0, 9, 7, 6, 0, 15, 1, 9, 5, 10, 0, 14, 4, 14, 6, 8, 0, 22, 0, 6, 9, 13, 5, 16, 0, 11, 5, 15, 0, 24, 0, 9, 9, 13, 3, 18, 0, 20, 8

Offset

1,4

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Formula

a(n) = pi(sigma(n)) - pi(n) = A000720(A000203(n)) - A000720(n).

Example

n = 12: sigma(n) = 28, pi(28) - pi(12) = 9 - 5 = 4.

Mathematica

Table[PrimePi[DivisorSigma[1, n]]-PrimePi[n], {n, 90}] (* Harvey P. Dale, Aug 18 2015 *)

Prog

(PARI) a(n) = primepi(sigma(n)) - primepi(n); \\ Michel Marcus, Dec 15 2013

Crossrefs

Cf. A000720, A000203, A070803, A070804, A085342-A085347.

Sequence in context: A161840 A355851 A140302 * A221474 A160812 A338271

Adjacent sequences: A085338 A085339 A085340 * A085342 A085343 A085344

Keyword

nonn

Author

Labos Elemer, Jul 10 2003

Status

approved