cp's OEIS Frontend

A218980 Integers not in A218852.

%I A218980 #15 Nov 10 2012 14:34:03
%S A218980 1,2,3,4,6,8,9,11,12,17,18,22,23,24,29,30,36,37,41,47,48,53,59,60,67,
%T A218980 71,72,79,83,89,97,101,107,113,120,127,131,137,144,149,157,163,167,
%U A218980 173,179,180,191,197,210,211,223,227,233,239,240,251,257,263,269,277
%N A218980 Integers not in A218852.
%C A218980 Conjecture: This sequence is infinite.
%o A218980 (JavaScript)
%o A218980 function divisorSum(n) {
%o A218980 c=0;
%o A218980 for (i=1;i<=n;i++) if (n%i==0) c+=i;
%o A218980 return c;
%o A218980 }
%o A218980 ds=new Array();
%o A218980 for (j=1;j<1001;j++) ds[j]=divisorSum(j);
%o A218980 a=new Array();
%o A218980 ac=0;
%o A218980 for (j=1;j<300;j++)
%o A218980 for (k=1;k<=j;k++)
%o A218980 for (m=1;m<=k;m++)
%o A218980 if (ds[j]+ds[k]+ds[m]==ds[j+k+m]) a[ac++]=j+k+m;
%o A218980 a.sort(function(a, b) {return a-b;});
%o A218980 i=0;
%o A218980 while(i++<a.length-1)
%o A218980 if (a[i]==a[i+1]) a.splice(i--,1);
%o A218980 document.writeln(a);
%o A218980 b=new Array();
%o A218980 ac=0;
%o A218980 bc=0;
%o A218980 for (i=0;i<a[a.length-1];i++) if (a[ac]!=i) b[bc++]=i; else ac++;
%o A218980 document.writeln(b);
%Y A218980 Cf. A218852.
%K A218980 nonn
%O A218980 1,2
%A A218980 _Jon Perry_, Nov 08 2012