1,18

Table of n, a(n) for n=1..86.

Marc Deléglise, Bounds for the density of abundant integers, Experiment. Math. Volume 7, Issue 2 (1998), 137-143.

Charles R. Wall, Phillip L. Crews and Donald B. Johnson, Density bounds for the sum of divisors function, Math. Comp. 26 (1972), 773-777.

Eric Weisstein's World of Mathematics, Abundant Number

A091194[1]=0; A091194[n_]:=A091194[n]=A091194[n-1]+Boole[DivisorSigma[1, n]>2n];

(* Recursive expression with data kept in memory; Enrique Pérez Herrero, Aug 14 2010 *)

(PARI) (n) = sum(k=1, n, sigma(k)/k > 2); \\ Michel Marcus, Apr 02 2015

Cf. A005101, A091195.

Sequence in context: A122027 A112751 A283297 * A156079 A268708 A061555

Adjacent sequences: A091191 A091192 A091193 * A091195 A091196 A091197

nonn

Reinhard Zumkeller, Dec 27 2003

approved