A063885 z(sigma(n)) = 2n, where z(n) = A048146.

24, 1536, 1631, 47360, 82458

Offset

1,1

Links

Table of n, a(n) for n=1..5.

Prog

(PARI) u(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d));
z(n) = sigma(n)-u(n);
for(n=1, 10^7, if(z(sigma(n))==2*n, print1(n, ", ")))

Crossrefs

Cf. A000203, A034448, A048146, A019284.

Sequence in context: A035174 A288955 A203973 * A019284 A333042 A112389

Adjacent sequences: A063882 A063883 A063884 * A063886 A063887 A063888

Keyword

nonn,more

Author

Jason Earls, Aug 28 2001

Status

approved