A072612 Minimal value of { abs(n-sigma(k)) : k>0 }.

0, 1, 0, 0, 1, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0, 1, 1, 0, 1, 0, 1, 2, 1, 0, 1, 2, 1, 0, 1, 0, 0, 0, 1, 2, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 2, 1, 0, 1, 2, 3, 2, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 2, 3, 1, 0, 1, 2, 1, 0, 1, 0, 1, 2, 1, 0, 1, 0, 1, 2, 1, 0, 1, 2, 3, 2, 1, 0, 0, 1, 0, 1, 1, 0, 1, 0, 1, 2, 1, 0, 1, 0, 1

Offset: 1

Author

Benoit Cloitre, Aug 11 2002

Keywords

• easy
• nonn

Comments

a(A002191(k)) = 0

Programs

PARI

a(n)=vecmin(vector(n,k,abs(n-sigma(k))))

Formula

Conjecture : S(n) = sum( k=1, n, a(k) ) = n + O(sqrt(n)) and more precisely for n large enough : n - (5/2)*sqrt(n) < S(n) < n - (3/2)*sqrt(n)