A080848 a(n) = n*(mu(n)+2), where mu is the Moebius function (A008683).

3, 2, 3, 8, 5, 18, 7, 16, 18, 30, 11, 24, 13, 42, 45, 32, 17, 36, 19, 40, 63, 66, 23, 48, 50, 78, 54, 56, 29, 30, 31, 64, 99, 102, 105, 72, 37, 114, 117, 80, 41, 42, 43, 88, 90, 138, 47, 96, 98, 100, 153, 104, 53, 108, 165, 112, 171, 174, 59, 120, 61, 186, 126, 128, 195, 66

Offset: 1

Author

Reinhard Zumkeller, Feb 20 2003

Keywords

• nonn
• easy

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A008683, A080847, A080849.

Programs

Mathematica

a[n_] := n * (MoebiusMu[n]+2); Array[a, 100] (* Amiram Eldar, May 17 2025 *)

PARI

a(n) = n * (moebius(n)+2); \\ Amiram Eldar, May 17 2025

Scheme

(define (A080848 n) (* n (+ 2 (A008683 n)))) ;; Antti Karttunen, Jul 26 2017

Formula

n <= a(n) <= 3*n.

Sum_{n>=1} 1/a(n)^2 = (Pi^4 + 46)/(24*Pi^2). - Amiram Eldar, May 17 2025