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A091194 Number of abundant numbers <= n. 4
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 15, 15, 15, 15, 15, 15, 16, 16, 17, 17, 17, 17, 18, 18, 18 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,18

LINKS

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

MATHEMATICA

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 *)

PROG

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

CROSSREFS

Cf. A005101, A091195.

Sequence in context: A122027 A112751 A283297 * A156079 A268708 A061555

Adjacent sequences:  A091191 A091192 A091193 * A091195 A091196 A091197

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Dec 27 2003

STATUS

approved

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Last modified September 26 04:27 EDT 2017. Contains 292502 sequences.