

A219036


Numbers n such that sigma(n)  tau(n) is a perfect number.


0



7, 21, 25, 29, 246, 286, 2688, 4062, 33550337, 4294934526, 5658405646, 5726153206, 5726306566, 6987790105, 7533178601
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OFFSET

1,1


LINKS

Table of n, a(n) for n=1..15.


FORMULA

Numbers n such that sigma(n)  tau(n) is a perfect number.


MATHEMATICA

perfectQ[n_] := DivisorSigma[1, n] == 2*n; Select[Range[100000], perfectQ[DivisorSigma[1, #]  DivisorSigma[0, #]] &] (* T. D. Noe, Nov 13 2012 *)


CROSSREFS

Cf. A000396 (perfect numbers).
Sequence in context: A200935 A097182 A058525 * A063469 A155131 A160890
Adjacent sequences: A219033 A219034 A219035 * A219037 A219038 A219039


KEYWORD

nonn


AUTHOR

Zdenek Cervenka, Nov 13 2012


EXTENSIONS

25 and 29 added by T. D. Noe, Nov 13 2012
a(10)a(15) from Donovan Johnson, Nov 13 2012


STATUS

approved



