A072548 a(n) = sigma(n) mod PrimePi(n).

0, 0, 1, 0, 0, 0, 3, 1, 2, 2, 3, 2, 0, 0, 1, 4, 4, 4, 2, 0, 4, 6, 6, 4, 6, 4, 2, 0, 2, 10, 8, 4, 10, 4, 3, 2, 0, 8, 6, 3, 5, 2, 0, 8, 2, 3, 4, 12, 3, 12, 8, 6, 8, 8, 8, 0, 10, 9, 15, 8, 6, 14, 1, 12, 0, 11, 12, 1, 11, 12, 15, 11, 9, 19, 14, 12, 0, 14, 10, 11, 16, 15, 17, 16, 17, 5, 19, 18, 18

Offset: 2

Author

Labos Elemer, Aug 05 2002

Keywords

• nonn

Links

• Michael De Vlieger, Table of n, a(n) for n = 2..10000

Crossrefs

Cf. A000203, A000720, A073321, A073322, A073323, A073324.

Programs

Magma

[SumOfDivisors(n) mod (#PrimesUpTo(n)): n in [2..100]]; // Vincenzo Librandi, Dec 10 2018

Maple

with(numtheory): seq(modp(sigma(n),pi(n)),n=2..100); # Muniru A Asiru, Dec 10 2018

Mathematica

Table[Mod[DivisorSigma[1, w], PrimePi[w]], {w, 1, 128}]

PARI

a(n) = sigma(n) % primepi(n); \\ Michel Marcus, Dec 10 2018

Formula

a(n) = A000203(n) mod A000720(n).