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a(n) = smallest k such that A141501(k) = 2*n+1.
2

%I #5 Mar 30 2012 17:27:55

%S 1,2,4,6,12,30,24,72,60,144,120,180,240,360,1008,720,1440,840,1260,

%T 3780,7920,3360,10920,2520,7560,5040,10080,69300,15120,864864,92400,

%U 27720,60480,65520,617760,240240,55440,196560,110880,471240,166320,6177600

%N a(n) = smallest k such that A141501(k) = 2*n+1.

%C All terms of A141501 are odd.

%H Klaus Brockhaus, <a href="/A143474/b143474.txt">Table of n, a(n) for n=1..69</a>

%e First few terms of A141501 are 3, 5, 5, 7, 3, 9, 3, 7, 5, 7, 3, 11, ..., so a(1) to a(5) are 1, 2, 4, 6, 12.

%o (PARI) {m=6200000; z=42; v=vector(z); for(n=1, m, k=1; d=divisors(n); while(1, c=0; for(j=1, #d, if(d[j]<=k, c++)); if(k-c<=c, k++, break)); i=(k-1)/2; if(i<=z&&v[i]<1, v[i]=n)); j=1; while(j<=z&&v[j]>0, print1(v[j], ","); j++)}

%Y Cf. A141501.

%K nonn

%O 1,2

%A _Klaus Brockhaus_, Aug 21 2008