OFFSET
1,1
COMMENTS
Trivial solutions with sopfr(k) = k and thus r = 0 are excluded.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
For k = 200, sopfr(200) = 2+2+2+5+5 = 16; 200 == 8 (mod 16); and sopfr(16) = 2+2+2+2 = 8 = r.
MAPLE
sopfr:= proc(n) local t;
add(t[1]*t[2], t = ifactors(n)[2])
end proc:
filter:= proc(k) local m, r;
m:= sopfr(k);
r:= sopfr(m);
r > 0 and r < m and k - r mod m = 0
end proc:
select(filter, [$1..10000]); # Robert Israel, Dec 19 2024
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
J. M. Bergot, May 04 2011
EXTENSIONS
Extended by Ray Chandler, May 11 2011
STATUS
approved