OFFSET
1,1
COMMENTS
Solutions of the equations n = (sigma(n)-n)'.
a(12) > 5*10^9. - Michel Marcus, Nov 01 2014
There could be a relation with terms in A125246 and A228450, since some terms of these sequences are here also. - Michel Marcus, Oct 30 2014
a(14) > 10^11. - Giovanni Resta, May 29 2016
EXAMPLE
Sum of the aliquot parts of 284 is sigma(284) - 284 = 220 and the arithmetic derivative of 220 is 284.~
MAPLE
with(numtheory): P:= proc(q) local a, n, p; for n from 1 to q do
a:=(sigma(n)-n)*add(op(2, p)/op(1, p), p=ifactors(sigma(n)-n)[2]);
if n=a then print(n); fi; od; end: P(10^9);
PROG
(PARI) ad(n) = sum(i=1, #f=factor(n)~, n/f[1, i]*f[2, i]);
isok(n) = ad(sigma(n) - n) == n; \\ Michel Marcus, Oct 28 2014
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Paolo P. Lava, Oct 15 2014
EXTENSIONS
a(6)-a(11) from Michel Marcus, Oct 28 2014
a(12)-a(13) from Giovanni Resta, May 29 2016
STATUS
approved