OFFSET
1,1
EXAMPLE
First four arithmetic derivatives of 19164 are 25564, 31848, 58412, 61916 and sqrt(19164^2 + 25564^2 + 31848^2 + 58412^2 + 61916^2) = 96336.
MAPLE
with(numtheory);
Dr:=proc(w) local x, p; x:=w*add(op(2, p)/op(1, p), p=ifactors(w)[2]); end:
P:=proc(q, h) local a, b, k, n; for n from 2 to q do a:=n; b:=n^2;
for k from 1 to h do a:=Dr(a); b:=b+a^2; od; if type(sqrt(b), integer) then print(n);
fi; od; end: P(10^9, 4);
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Paolo P. Lava, Oct 21 2014
EXTENSIONS
a(4) from Ray Chandler, Dec 23 2016
a(5) from Ray Chandler, Jan 11 2017
STATUS
approved