

A057265


Even refactorable numbers (i.e., the number of divisors is itself a divisor and it is also even).


11



2, 8, 12, 18, 24, 40, 56, 60, 72, 80, 84, 88, 96, 104, 108, 128, 132, 136, 152, 156, 180, 184, 204, 228, 232, 240, 248, 252, 276, 288, 296, 328, 344, 348, 360, 372, 376, 384, 396, 424, 444, 448, 450, 468, 472, 480, 488, 492
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OFFSET

1,1


COMMENTS

Invented by the HR mathematical theory formation program.


REFERENCES

S. Colton, Unpublished PhD Thesis, University of Edinburgh, 2000


LINKS

Table of n, a(n) for n=1..48.
S. Colton, Refactorable Numbers  A Machine Invention, J. Integer Sequences, Vol. 2, 1999, #2.
S. Colton, HR  Automatic Theory Formation in Pure Mathematics


EXAMPLE

18 is refactorable because tau(18) = 6 and 6 divides 18 and 18 is even.


MATHEMATICA

rfnQ[n_]:=Module[{ds=DivisorSigma[0, n]}, Divisible[n, ds] && EvenQ[ds]]; Select[Range[2, 500, 2], rfnQ] (* Harvey P. Dale, Mar 14 2011 *)


CROSSREFS

Cf. A033950, A036896.
Sequence in context: A090772 A046525 A235353 * A099418 A108987 A035405
Adjacent sequences: A057262 A057263 A057264 * A057266 A057267 A057268


KEYWORD

easy,nonn


AUTHOR

Simon Colton (simonco(AT)cs.york.ac.uk), Aug 21 2000


EXTENSIONS

Corrected (erroneous term 36 removed) by Harvey P. Dale, Mar 14 2011


STATUS

approved



