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A264762 a(n) is the index of A246946(n) in A024619, integers x that satisfy omega(x) >= 2.

%I A264762 #12 Nov 26 2015 03:39:41
%S A264762 1,3,6,10,13,2,7,20,26,34,5,23,44,55,17,21,4,12,31,41,16,67,8,36,50,
%T A264762 25,29,38,9,22,54,70,30,113,14,63,86,42,47,11,28,66,85,37,136,19,76,
%U A264762 106,61,65,15,39,90,116,48,64,79,69,73,18,45,102,133,60,207,32,117,164
%N A264762 a(n) is the index of A246946(n) in A024619, integers x that satisfy omega(x) >= 2.
%C A264762 Is this a permutation of the positive integers?
%H A264762 Robert Israel, <a href="/A264762/b264762.txt">Table of n, a(n) for n = 1..10000</a>
%e A264762 The first 6 terms of A246946 are 6, 12, 18, 24, 30 and 10, that is, the 1st, 3rd, 6th, 10th, 13th and 2nd terms of A024619.
%p A264762 N:= 2000: # get all terms before the first term > N.
%p A264762 W:= Vector(N,t -> if nops(numtheory:-factorset(t))<=1 then 0 else 1 fi):
%p A264762 WS:= ListTools:-PartialSums(convert(W,list)):
%p A264762 m:= 1:
%p A264762 F:= {2,3}:
%p A264762 A[1]:= WS[6]:
%p A264762 W[6]:= 0:
%p A264762 for n from 2 do
%p A264762   while W[m] = 0 and m < N do m:= m+1 od;
%p A264762   for k from m to N do
%p A264762      if W[k] = 1 and nops(numtheory:-factorset(k) intersect F) = 2 then
%p A264762         A[n]:= WS[k];
%p A264762         W[k]:= 0;
%p A264762         F:= numtheory:-factorset(k);
%p A264762         break
%p A264762      fi
%p A264762   od;
%p A264762   if k > N then break fi;
%p A264762 od:
%p A264762 seq(A[i],i=1..n-1); # _Robert Israel_, Nov 23 2015
%o A264762 (PARI) v246946(nn) = {a = 6; fa = (factor(a)[,1])~; va = [a]; vs = va; k = 0; while (k!= nn, k = 1; while (!((#setintersect(fa, (factor(k)[,1])~) == 2) && (! vecsearch(vs, k))), k++); a = k; fa = (factor(a)[,1])~; va = concat(va, k); vs = vecsort(va);); va;}
%o A264762 v024619(nn) = {va = []; for (n=1, nn, if (omega(n) >= 2, va = concat(va, n));); va;}
%o A264762 lista(nn) = {v = v246946(nn); w = v024619(vecmax(v)); for (k=1, #v, for (j=1, #w, if (w[j] == v[k], print1(j, ", "); break);););}
%Y A264762 Cf. A024619, A246946.
%K A264762 nonn
%O A264762 1,2
%A A264762 _Michel Marcus_, Nov 23 2015