OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1000 (terms 1..100 from Harry J. Smith)
MATHEMATICA
sudsQ[n_]:=Module[{uds=Sort[Flatten[Outer[Times, Sequence@@({1, #}&/@ Power@@@FactorInteger[n^2])]]]}, IntegerQ[Sqrt[Total[uds]]]]; Join[{1}, Select[Range[230000], sudsQ]] (* Harvey P. Dale, Dec 09 2011 *)
PROG
(PARI) {usigma(n, s=1, fac, i)= fac=factor(n); for(i=1, matsize(fac)[1], s=s*(1+fac[i, 1]^fac[i, 2]); ); return(s); }
for(n=1, 10^6, if(issquare(usigma(n^2)), print1(n, " ")))
(PARI) usigma(n)= { local(f, s=1); f=factor(n); for(i=1, matsize(f)[1], s*=1 + f[i, 1]^f[i, 2]); return(s) }
{ n=0; for (m=1, 10^9, if (issquare(usigma(m^2)), write("b064498.txt", n++, " ", m); if (n==100, break)) ) } \\ Harry J. Smith, Sep 16 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Earls, Oct 05 2001
STATUS
approved