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%I #31 Mar 12 2015 23:24:55
%S 1,4,15,20,30,48,84,160,144,210,462,240,624,1134,480,864,1836,720,
%T 8740,840,1512,2376,4968,2400,3900,3120,4536,4032,15312,2520,17856,
%U 5280,6930,10710,15400,7200,47952,17100,12480,7920,72324,9240,43344,16632,20790
%N a(n) = smallest k such that n is the n-th largest divisor of k.
%C The smallest row k such that n is the n-th entry in the triangle A056538 of divisors in reverse order.
%C Is a(n) defined for every n ? - _Giovanni Resta_, May 15 2013
%H Alois P. Heinz and Zak Seidov, <a href="/A225562/b225562.txt">Table of n, a(n) for n = 1..1000</a> (first 200 terms from Alois P. Heinz)
%e a(6) = 48 because the divisors of 48 are {48, 24, 16, 12, 8, 6, 4, 3, 2, 1} and 6 is the 6th divisor of 48.
%p with(numtheory):
%p a:= proc(n) local k;
%p for k from n by n while tau(k)<n or
%p sort([divisors(k)[]], `>`)[n]<>n do od; k
%p end:
%p seq(a(n), n=1..50); # _Alois P. Heinz_, May 29 2013
%t a[n_] := Block[{k = 1, d}, While[Length[d = Reverse@ Divisors@ k] < n || n != d[[n]], k++]; k]; Array[a, 20] (* _Giovanni Resta_, May 15 2013 *)
%K nonn
%O 1,2
%A _Irina Gerasimova_, May 13 2013
%E a(13)-a(45) from _Giovanni Resta_, May 15 2013
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