A073771 - OEIS

%I #9 Mar 24 2024 04:25:44

%S 4,36,48,240,720,1680,15120,20160,45360,50400,221760,498960,554400,

%T 665280,2882880,6486480,14414400,17297280,32432400,43243200,110270160,

%U 245044800,294053760,735134400,2095133040,2205403200,4655851200

%N Highly composite numbers k such that 2*k is not a highly composite number.

%C The terms were determined by means of A. Flammenkamp's list (cf. Links); the terms <= 17297280 were confirmed by a PARI program.

%H Achim Flammenkamp <a href="http://wwwhomes.uni-bielefeld.de/achim/highly.html">Highly Composite Numbers</a>.

%e 36 = A002182(7) is a term since 2*36 = 72 is not highly composite.

%o (PARI) {a=1; v=[1]; for(k=1,40000000,b=numdiv(k); if(b>a,a=b; v=concat(v,k); while(2*v[1]<=k,if(2*v[1]<k,print1(v[1],",")); v=vecextract(v,"2.."))))}

%Y Cf. A002182, A072938.

%K nonn

%O 1,1

%A _Klaus Brockhaus_, Aug 19 2002