OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..250 (terms 1..100 from Harry J. Smith)
MATHEMATICA
usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger@n); um = 0; s = {}; Do[u = usigma[n]; If[IntegerQ@Sqrt[u] && u > um, um = u; AppendTo[s, n]], {n, 1, 10^5}]; s (* Amiram Eldar, Jul 29 2019 *)
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); a=0; j=[]; for(n=1, 10^5, x=usigma(n); if(issquare(x), b=x; if(b>a, a=b; j=concat(j, n)))); j
(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=a=0; for (m=1, 10^9, if (issquare(b=usigma(m)), if(b>a, a=b; write("b064443.txt", n++, " ", m); if (n==100, break))) ) } \\ Harry J. Smith, Sep 14 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Earls, Oct 01 2001
STATUS
approved