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

%I A327328 #37 Mar 03 2020 08:46:34
%S A327328 1,3,6,12,18,45,30,105,72,60,90,315,120,3645,210,180,450,1575,480,
%T A327328 2835,360,420,630,3465,900,720,7290,1620,840,14175,1440,10395,1800,
%U A327328 1260,3150,1680,3240,1937102445,5670,14580,3600,127575,3360,2066715,2520,3780,6930
%N A327328 a(n) is the smallest positive integer divisible by exactly n nonpowers of 2.
%C A327328 Terms are of the form A233819(m) * 2^k for some m > 0, k >= 0. - _David A. Corneth_, Nov 25 2019
%H A327328 David A. Corneth, <a href="/A327328/b327328.txt">Table of n, a(n) for n = 0..1000</a>
%o A327328 (PARI) ispp(x) = my(p); (x == 1) || (isprimepower(x, &p) && (p==2));
%o A327328 nbdiv(k) = #select(x->(!ispp(x)), divisors(k));
%o A327328 a(n) = my(k=1); while (nbdiv(k) != n, k++); k; \\ _Michel Marcus_, Nov 25 2019
%o A327328 (PARI) a(n) = for(i = 1, oo, if(numdiv(i) - valuation(i, 2) - 1 == n, return(i))) \\ _David A. Corneth_, Nov 25 2019
%Y A327328 Cf. A057716, A233819, A326987, A326989.
%K A327328 nonn
%O A327328 0,2
%A A327328 _Omar E. Pol_, Sep 20 2019
%E A327328 a(13)-a(36), a(38)-a(46) from _Jon E. Schoenfield_, Nov 22 2019
%E A327328 a(37) from _Jon E. Schoenfield_ and _David A. Corneth_, Nov 25 2019