A327328 - OEIS

%I #37 Mar 03 2020 08:46:34

%S 1,3,6,12,18,45,30,105,72,60,90,315,120,3645,210,180,450,1575,480,

%T 2835,360,420,630,3465,900,720,7290,1620,840,14175,1440,10395,1800,

%U 1260,3150,1680,3240,1937102445,5670,14580,3600,127575,3360,2066715,2520,3780,6930

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

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

%H David A. Corneth, <a href="/A327328/b327328.txt">Table of n, a(n) for n = 0..1000</a>

%o (PARI) ispp(x) = my(p); (x == 1) || (isprimepower(x, &p) && (p==2));

%o nbdiv(k) = #select(x->(!ispp(x)), divisors(k));

%o a(n) = my(k=1); while (nbdiv(k) != n, k++); k; \\ _Michel Marcus_, Nov 25 2019

%o (PARI) a(n) = for(i = 1, oo, if(numdiv(i) - valuation(i, 2) - 1 == n, return(i))) \\ _David A. Corneth_, Nov 25 2019

%Y Cf. A057716, A233819, A326987, A326989.

%K nonn

%O 0,2

%A _Omar E. Pol_, Sep 20 2019

%E a(13)-a(36), a(38)-a(46) from _Jon E. Schoenfield_, Nov 22 2019

%E a(37) from _Jon E. Schoenfield_ and _David A. Corneth_, Nov 25 2019