OFFSET
1,12
COMMENTS
LINKS
Matthew House, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Abundance
MAPLE
f:= proc(n) local r;
r:= numtheory:-sigma(n) - 2*n;
if r <= 0 then 0
else nops(select(`<=`, numtheory:-divisors(n), r))
fi
end proc:
map(f, [$1..100]); # Robert Israel, Jul 27 2015
MATHEMATICA
Table[Count[Divisors@ n, x_ /; x <= DivisorSigma[1, n] - 2 n], {n,
120}] (* Michael De Vlieger, Jul 27 2015 *)
PROG
(PARI) a(n) = my(ab = sigma(n) - 2*n); sumdiv(n, d, d <= ab); \\ Michel Marcus, Jul 27 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Dec 27 2003
STATUS
approved