A244327 a(n) = floor((n*(n+1)/2) / sigma(n)) = floor(A000217(n) / A000203(n)).

1, 1, 1, 1, 2, 1, 3, 2, 3, 3, 5, 2, 6, 4, 5, 4, 8, 4, 9, 5, 7, 7, 11, 5, 10, 8, 9, 7, 14, 6, 15, 8, 11, 11, 13, 7, 18, 12, 13, 9, 20, 9, 21, 11, 13, 15, 23, 9, 21, 13, 18, 14, 26, 12, 21, 13, 20, 19, 29, 10, 30, 20, 19, 16, 25, 15, 33, 18, 25, 17, 35, 13, 36

Offset

1,5

Comments

RECORD transform of a(n) is A140475 (union of number 1 and primes >= 5).

Sequence of numbers n such that a(n) = a(n+1) = A244666.

Links

Alois P. Heinz, Table of n, a(n) for n = 1..20000

Formula

a(n) = A244328(n) + A244329(n) for n >= 7.

Example

For n = 10; a(10) = floor(A000217(10) / A000203(10)) = floor(55 / 18) = 3.

Maple

a:= n-> floor(n*(n+1)/(2*numtheory[sigma](n))):
seq(a(n), n=1..100);  # Alois P. Heinz, Mar 28 2018

Mathematica

A244327[n_] := Floor[n*(n + 1)/(2*DivisorSigma[1, n])];
Array[A244327, 100] (* Paolo Xausa, Sep 01 2024 *)

Prog

(Magma) [Floor((n*(n+1)div 2) div (SumOfDivisors(n))): n in [1..1000]];

Crossrefs

Cf. A000203, A000217, A024816, A244328, A244329, A244666.

Sequence in context: A267806 A025797 A035386 * A319318 A029164 A364350

Adjacent sequences: A244324 A244325 A244326 * A244328 A244329 A244330

Keyword

nonn

Author

Jaroslav Krizek, Jul 08 2014

Status

approved