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A175334 a(n) is the smallest positive divisor of Product_{k=1..n} d(k) that does not yet occur in the sequence, where d(k) is the number of positive divisors of k. 1
1, 2, 4, 3, 6, 8, 12, 16, 9, 18, 24, 27, 32, 36, 48, 5, 10, 15, 20, 30, 40, 45, 54, 60, 64, 72, 80, 81, 90, 96, 108, 120, 128, 135, 144, 160, 162, 180, 192, 216, 240, 243, 256, 270, 288, 320, 324, 25, 50, 75, 100, 150, 200, 225, 300, 360, 384, 400, 405, 432, 450, 480 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This sequence is a permutation of the positive integers.

LINKS

Table of n, a(n) for n=1..62.

MAPLE

From R. J. Mathar, Aug 31 2010: (Start)

A066843 := proc(n) option remember; if n <= 2 then n; else procname(n-1) * numtheory[tau](n) ; end if; end proc:

A175334 := proc(n) option remember ; dvs := sort(convert(numtheory[divisors](A066843(n)), list)) ; for d in dvs do wrks := true; for i from 1 to n-1 do if procname(i) = d then wrks := false; break; end if; end do: if wrks then return d; end if; end do: end proc:

seq(A175334(n), n=1..90) ; (End)

CROSSREFS

Cf. A066843.

Sequence in context: A039874 A193991 A114107 * A128556 A212485 A077661

Adjacent sequences:  A175331 A175332 A175333 * A175335 A175336 A175337

KEYWORD

nonn

AUTHOR

Leroy Quet, Apr 14 2010

EXTENSIONS

More terms from R. J. Mathar, Aug 31 2010

STATUS

approved

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Last modified August 12 17:17 EDT 2020. Contains 336439 sequences. (Running on oeis4.)