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%I #15 Sep 26 2018 04:51:16
%S 1,1,2,1,4,1,6,2,4,3,10,1,12,5,6,2,16,2,18,3,10,11,22,1,15,13,14,5,28,
%T 2,30,7,18,19,20,1,36,22,23,4,40,5,42,11,12,28,46,1,33,14,31,15,52,7,
%U 34,8,36,37,58,1,60,39,19,10,42,10,66,22,45,11,70,2,72,48,25,26,51,13,78,4
%N a(n) = number of positive integers k, k <= n, where d(k) >= d(n); d(n) = number of positive divisors of n.
%H Robert Israel, <a href="/A138009/b138009.txt">Table of n, a(n) for n = 1..10000</a>
%e 9 has 3 positive divisors. Among the first 9 positive integers, there are four that have more than or equal the number of divisors than 9 has: 4, with 3 divisors; 6, with 4 divisors; 8, with 4 divisors; and 9, with 3 divisors. So a(9) = 4.
%p L:= [2]: A[1]:= 1:
%p for n from 2 to 100 do
%p v:= 2*numtheory:-tau(n);
%p k:= ListTools:-BinaryPlace(L,v-1);
%p A[n]:= n-k;
%p L:= [op(L[1..k]),v,op(L[k+1..-1])];
%p od:
%p seq(A[i],i=1..100); # _Robert Israel_, Sep 26 2018
%t Table[Length[Select[Range[n], Length[Divisors[ # ]]>=Length[Divisors[n]]&]], {n,1,100}] (* _Stefan Steinerberger_, Feb 29 2008 *)
%o (PARI) a(n) = my(dn=numdiv(n)); sum(k=1, n, numdiv(k) >= dn); \\ _Michel Marcus_, Sep 26 2018
%Y Cf. A079788, A067004.
%K nonn,look
%O 1,3
%A _Leroy Quet_, Feb 27 2008
%E More terms from _Stefan Steinerberger_, Feb 29 2008
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