OFFSET
1,2
COMMENTS
LINKS
Paolo P. Lava, Table of n, a(n) for n = 1..1000
EXAMPLE
a(20) = 1 because the 20th deficient number is 25 and:
1) f(25) = sigma(25) - 25 = 6 < 25.
We must stop here because 6 is abundant.
a(21) = 7 because the 21st deficient number is 26 and:
1) f(26) = sigma(26) - 26 = 16 < 26;
2) f(16) = sigma(16) - 16 = 15 < 16;
3) f(15) = sigma(15) - 15 = 9 < 15;
4) f(9) = sigma(9) - 9 = 4 < 9;
5) f(4) = sigma(4) - 4 = 3 < 4;
6) f(3) = sigma(3) - 3 = 2 < 1;
7) f(1) = sigma(1) - 1 = 0 < 1.
We must stop here because sigma(0) is not defined.
MAPLE
with(numtheory): P:=proc(q) local a, b, n, t;
for n from 1 to q do t:=0; b:=sigma(n)-n; a:=n;
if b<a then while b<a do t:=t+1; a:=b; b:=sigma(b)-b; od;
print(t); fi; od; end: P(10^3);
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Feb 03 2015
STATUS
approved