A327328 a(n) is the smallest positive integer divisible by exactly n nonpowers of 2.

1, 3, 6, 12, 18, 45, 30, 105, 72, 60, 90, 315, 120, 3645, 210, 180, 450, 1575, 480, 2835, 360, 420, 630, 3465, 900, 720, 7290, 1620, 840, 14175, 1440, 10395, 1800, 1260, 3150, 1680, 3240, 1937102445, 5670, 14580, 3600, 127575, 3360, 2066715, 2520, 3780, 6930

Offset: 0

Author

Omar E. Pol, Sep 20 2019

Keywords

• nonn

Comments

Terms are of the form A233819(m) * 2^k for some m > 0, k >= 0. - David A. Corneth, Nov 25 2019

Links

• David A. Corneth, Table of n, a(n) for n = 0..1000

Crossrefs

Cf. A057716, A233819, A326987, A326989.

Programs

PARI

ispp(x) = my(p); (x == 1) || (isprimepower(x, &p) && (p==2));
nbdiv(k) = #select(x->(!ispp(x)), divisors(k));
a(n) = my(k=1); while (nbdiv(k) != n, k++); k; \\ Michel Marcus, Nov 25 2019

PARI

a(n) = for(i = 1, oo, if(numdiv(i) - valuation(i, 2) - 1 == n, return(i))) \\ David A. Corneth, Nov 25 2019

Extensions

a(13)-a(36), a(38)-a(46) from Jon E. Schoenfield, Nov 22 2019

a(37) from Jon E. Schoenfield and David A. Corneth, Nov 25 2019