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, 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

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: A368523 A114107 A362041 * 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