A152991 -id:A152991 - cp's OEIS frontend

A152992 a(n) = sigma(n) - d(n) - pi(n).

0, 0, 0, 2, 1, 5, 2, 7, 6, 10, 5, 17, 6, 14, 14, 20, 9, 26, 10, 28, 20, 24, 13, 43, 19, 29, 27, 41, 18, 54, 19, 46, 33, 39, 33, 71, 24, 44, 40, 70, 27, 75, 28, 64, 58, 54, 31, 99, 39, 72, 53, 77, 36, 96, 52, 96, 60, 70, 41, 139, 42, 74, 80, 102, 62, 118, 47, 101, 73, 117, 50

Offset: 1

Omar E. Pol, Dec 19 2008, Dec 31 2008

			a(15) = 24 - 4 - 6 = 14 because the sum of divisors of 15 is 1 + 3 + 5 + 15 = 24, the number of divisors of 15 is 4 (1,3,5,15) and the number of primes not exceeding 15 is 6 (2,3,5,7,11,13). - _Emeric Deutsch_, Dec 30 2008

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

Cf. A000005, A000203, A000720, A065608, A152770, A152991.

with(numtheory): seq(sigma(n)-tau(n)-pi(n), n = 1 .. 75); # Emeric Deutsch, Dec 30 2008

Table[DivisorSigma[1,n]-DivisorSigma[0,n]-PrimePi[n],{n,75}] (* Harvey P. Dale, Sep 19 2011 *)

a(n) = A000203(n) - A000005(n) - A000720(n) = A065608(n) - A000720(n) = A152991(n) - A000005(n).

Corrected and extended by Emeric Deutsch, Dec 30 2008

A152993 a(n) = n - d(n) - pi(n) + 1.

Original entry on oeis.org

1, 0, 0, 0, 1, 0, 2, 1, 3, 3, 5, 2, 6, 5, 6, 6, 9, 6, 10, 7, 10, 11, 13, 8, 14, 14, 15, 14, 18, 13, 19, 16, 19, 20, 21, 17, 24, 23, 24, 21, 27, 22, 28, 25, 26, 29, 31, 24, 32, 30, 33, 32, 36, 31, 36, 33, 38, 39, 41, 32, 42, 41, 40, 40, 44, 41, 47, 44, 47, 44

Offset: 1

Omar E. Pol, Dec 19 2008

Andrew Howroyd, Table of n, a(n) for n = 1..1000

Cf. A000005, A000720, A152770, A152991, A152992.

Table[n-DivisorSigma[0,n]-PrimePi[n]+1,{n,70}] (* Harvey P. Dale, Sep 16 2020 *)

a(n) = {n - numdiv(n) - primepi(n) + 1} \\ Andrew Howroyd, Jan 03 2020

a(n) = n - A000005(n) - A000720(n) + 1.

Terms a(17) and beyond from Andrew Howroyd, Jan 03 2020

cp's OEIS Frontend

A152992 a(n) = sigma(n) - d(n) - pi(n).

Views

Author

Keywords

Examples

Links

Crossrefs

Programs

Maple

Mathematica

Formula

Extensions