OFFSET
1,1
EXAMPLE
First three arithmetic derivatives of 1808 are 3632, 7280, 17616 and sqrt(1808^2 + 3632^2 + 7280^2 + 17616^2) = 19488.
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, 3);
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Paolo P. Lava, Oct 21 2014
EXTENSIONS
a(13) from Ray Chandler, Dec 23 2016
a(14) from Ray Chandler, Dec 24 2016
a(15) from Ray Chandler, Jan 08 2017
STATUS
approved