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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified March 26 23:02 EDT 2019. Contains 321565 sequences. (Running on oeis4.)