login
A219179
Numbers n such that sigma(n)/tau(n) is a perfect number.
0
11, 14, 15, 91, 92, 132, 140, 991, 1891, 3525, 3792, 4025, 4650, 5775, 6384, 45847, 78337, 99904, 105664, 180544, 133152769, 134176771, 227512999, 233016679, 451443979, 865079296, 1478127616, 1509765120, 1585188864, 1660973056, 1793101824, 3063803904
OFFSET
1,1
MATHEMATICA
perfectQ[n_] := DivisorSigma[1, n] == 2*n; Select[Range[10000], perfectQ[DivisorSigma[1, #] / DivisorSigma[0, #]] &] (* T. D. Noe, Nov 13 2012 *)
CROSSREFS
Subsequence of A003601.
Cf. A000396 (perfect numbers).
Sequence in context: A061743 A038630 A239935 * A221281 A025058 A025060
KEYWORD
nonn
AUTHOR
Zdenek Cervenka, Nov 13 2012
EXTENSIONS
a(21)-a(32) from Donovan Johnson, Nov 13 2012
STATUS
approved