OFFSET
1,1
COMMENTS
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MAPLE
with(numtheory): for n from 1 to 2000 do :it:=1:s:=0:x:=divisors(n): n1:=nops(x): for k from 1 to n1 do:d:=x[k]:if gcd(d, n/d)=1 then s:=s+d:else fi:od: s1:=sigma(n): if sqrt(s1-s)=floor(sqrt(s1-s)) and s1>s then printf(`%d, `, n):else fi:od:
MATHEMATICA
lst={}; usigma[n_] := Block[{d=Divisors[n]}, DivisorSigma[1, n] - Plus@@Select[d, GCD[#, n/#] == 1&]]; Do[If[IntegerQ[Sqrt[usigma[n] && usigma[n] > 0]], AppendTo[lst, n]], {n, 2000}]; lst
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Mar 15 2013
STATUS
approved