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If n is the k-th composite number then a(n) = a(k), otherwise a(n) = n.
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%I #13 Jul 11 2022 02:39:02

%S 1,2,3,1,5,2,7,3,1,5,11,2,13,7,3,1,17,5,19,11,2,13,23,7,3,1,17,5,29,

%T 19,31,11,2,13,23,7,37,3,1,17,41,5,43,29,19,31,47,11,2,13,23,7,53,37,

%U 3,1,17,41,59,5,61,43,29,19,31,47,67,11,2,13,71,23,73

%N If n is the k-th composite number then a(n) = a(k), otherwise a(n) = n.

%H Rémy Sigrist, <a href="/A328661/b328661.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = 1 iff n belongs to A006508.

%e a(42) = a(28) = a(18) = a(10) = a(5) = 5.

%o (PARI) k=0; for (n=1, #a=vector(73), print1 (a[n] = if (bigomega(n)>1, a[k++], n) ", "))

%Y See A288469 and A328018 for similar sequences.

%Y Cf. A002808, A006508.

%K nonn

%O 1,2

%A _Rémy Sigrist_, Oct 24 2019