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

0,2

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

Prog

(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

Crossrefs

Cf. A057716, A233819, A326987, A326989.

Sequence in context: A356020 A341316 A298029 * A356019 A363463 A074899

Adjacent sequences: A327325 A327326 A327327 * A327329 A327330 A327331

Keyword

nonn

Author

Omar E. Pol, Sep 20 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

Status

approved