OFFSET
1,2
COMMENTS
a(17) > 1e9.
10^11 < a(24) <= 209584184160. a(25) <= 210197601120. - Donovan Johnson, Mar 12 2011
a(28) > 3*10^11. - Giovanni Resta, Aug 14 2019
MATHEMATICA
lst = {}; k = 1; While[k < 10^9, If[ BitXor @@ Divisors@k == k, AppendTo[lst, k]; Print@k]; k++ ]; lst (* Robert G. Wilson v, Jun 27 2010 *)
PROG
(PARI) xigma(n)=local(ds, r); ds=divisors(n); for(k=1, #ds, r=bitxor(r, ds[k])); r
for(n=1, 1000000000, if(xigma(n)==n, print1(n", ")))
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Franklin T. Adams-Watters, Jun 22 2010
EXTENSIONS
a(17) from Robert G. Wilson v, Jul 30 2010
a(18)-a(23) from Donovan Johnson, Mar 12 2011
a(24)-a(27) from Giovanni Resta, Aug 14 2019
STATUS
approved