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

Author

Leroy Quet, Apr 14 2010

Keywords

• nonn

Comments

This sequence is a permutation of the positive integers.

Crossrefs

Cf. A066843.

Programs

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)

Extensions

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