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A097215 Numbers n such that A076078(n)=n and bigomega(n) >= 2; or in other words, A097214, excluding powers of 2. 3
10, 44, 184, 752, 12224, 49024, 61064, 981520, 12580864, 206158168064, 16492668126208, 1080863908958322688, 18374686467592175488, 885443715520878608384, 4703919738602662723328 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A076078(n) equals the number of sets of distinct positive integers with a least common multiple of n.

If 3*2^m-1 is an odd prime then 2^m*(3*2^m-1) is in the sequence. - Farideh Firoozbakht, May 03 2009

For what seems to be an appearance of this sequence in a different context, see Harborth (2013). - N. J. A. Sloane, Jun 08 2013

LINKS

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

F. Firoozbakht, M. F. Hasler, Variations on Euclid's formula for Perfect Numbers, JIS 13 (2010) #10.3.1.

Heiko Harborth, On h-perfect numbers, Annales Mathematicae et Informaticae, 41 (2013) pp. 57-62.

EXAMPLE

For example, there are 184 sets of distinct positive integers with a least common multiple of 184.

MATHEMATICA

f[n_] := Block[{d = Divisors[n]}, Plus @@ (MoebiusMu[n/d](2^DivisorSigma[0, d] - 1))]; t = Union[ Table[ f[n], {n, 28000000}]]; Select[t, f[ # ] == # && !IntegerQ[ Log[2, # ]] &] (* Robert G. Wilson v, Aug 17 2004 *)

CROSSREFS

Cf. A097214, A097416.

Cf. A002235. - Farideh Firoozbakht, May 03 2009

Sequence in context: A220994 A097416 A076373 * A281993 A126397 A164607

Adjacent sequences:  A097212 A097213 A097214 * A097216 A097217 A097218

KEYWORD

nonn

AUTHOR

Matthew Vandermast, Aug 12 2004

EXTENSIONS

More terms from Robert G. Wilson v, Aug 18 2004

STATUS

approved

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Last modified November 22 05:36 EST 2017. Contains 295076 sequences.