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%I #18 May 13 2023 13:41:16
%S 1,1,1,2,1,1,1,2,1,1,1,2,1,1,3,1,2,1,1,1,2,1,3,1,1,2,1,1,1,2,1,1,4,1,
%T 2,1,1,3,1,2,1,1,1,2,1,3,1,1,2,1,1,1,2,1,4,1,1,2,1,1,3,1,2,1,1,4,1,2,
%U 1,3,1,1,2,1,1,1,2,1,1,1,2,1,1,3,1,2,1,4,1,5,1,2,1,3,1,1,2,1,1,4,1,2,1,1,1,2
%N Index of the least prime dividing the n-th composite number: A000720(A020639(A002808(n))).
%H Harvey P. Dale, <a href="/A118663/b118663.txt">Table of n, a(n) for n = 1..1000</a>
%F A118663 = A000720 o A056608. - _M. F. Hasler_, Apr 03 2012
%t PrimePi[FactorInteger[#][[1,1]]]&/@Select[Range[200],CompositeQ] (* _Harvey P. Dale_, May 13 2023 *)
%o (PARI) for(i=2,999,isprime(i)||print1(primepi(factor(i)[1,1])",")) \\ - _M. F. Hasler_, Apr 03 2012
%Y Cf. A056608.
%K easy,nonn
%O 1,4
%A _Giovanni Teofilatto_, May 19 2006
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