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A128556 a(1)=1. a(n) = the smallest positive multiple of d(a(n-1)) that does not occur earlier in the sequence, where d(m) is the number of positive divisors of m.

%I A128556 #9 Apr 09 2014 10:13:42
%S A128556 1,2,4,3,6,8,12,18,24,16,5,10,20,30,32,36,9,15,28,42,40,48,50,54,56,
%T A128556 64,7,14,44,60,72,84,96,108,120,80,70,88,104,112,90,132,144,45,66,128,
%U A128556 136,152,160,156,168,176,100,27,52,78,184,192,98,102,200,180
%N A128556 a(1)=1. a(n) = the smallest positive multiple of d(a(n-1)) that does not occur earlier in the sequence, where d(m) is the number of positive divisors of m.
%C A128556 Is this sequence is a permutation of the positive integers?
%H A128556 Diana Mecum, <a href="/A128556/b128556.txt">Table of n, a(n) for n = 1..1000</a>
%e A128556 a(9) = 24 has 8 positive divisors. So a(10) is the smallest positive multiple of 8 that has yet to appear in the sequence. 8 occurs among the first 9 terms of the sequence, but 16 does not. So a(10) = 16.
%Y A128556 Cf. A128555.
%K A128556 nonn
%O A128556 1,2
%A A128556 _Leroy Quet_, Mar 10 2007
%E A128556 More terms from _Diana L. Mecum_, May 29 2007