OFFSET
1,1
COMMENTS
The asymptotic density of this sequence is > 1/a(1) ~ 8*10^(-9). Wall et al. (1972) proved that it is < 0.0122. - Amiram Eldar, Feb 13 2021
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..10000
Richard Laatsch, Measuring the Abundancy of Integers, Mathematics Magazine, Vol. 59, No. 2 (1986), pp. 84-92, alternative link.
Gordon L. Miller and Mary T. Whalen, Multiply Abundant Numbers, School Science and Mathematics, Volume 95, Issue 5 (May 1995), pp. 256-259.
Charles R. Wall, Phillip L. Crews and Donald B. Johnson, Density Bounds for the Sum of Divisors Function, Mathematics of Computation, Vol. 26, No. 119 (1972), pp. 773-777; Errata, Vol. 31, No. 138 (1977), p. 616.
FORMULA
A001221(a(n)) >= 6 (Laatsch, 1986). - Amiram Eldar, Nov 07 2020
EXAMPLE
sigma(122522400) = 614210688 and 614210688 > 5 * 122522400.
PROG
(PARI) for(n=122522400, 563603040, if(sigma(n)>5*n, print1(n ", ")))
CROSSREFS
KEYWORD
nonn
AUTHOR
Donovan Johnson, Aug 07 2012
STATUS
approved