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%I #11 Jul 29 2019 17:01:18
%S 1,2,3,4,9,5,6,7,15,8,18,10,21,11,12,25,13,27,14,30,16,33,17,35,36,19,
%T 39,20,42,22,45,23,24,49,50,51,26,54,55,28,57,29,60,31,63,32,65,66,34,
%U 69,70,72,37,75,38,77,78,40,81,41,84,85,43,87,44,90,91
%N a(n) is the smallest divisor of the n-th nonprime number (A018252(n)) not already in the sequence.
%C This sequence is a permutation of the natural numbers.
%C Empirically:
%C - the subsequence with the terms satisfying a(n) <= n correspond to A093641,
%C - if a(n) > n, then a(n) = A018252(n),
%C - these two situations appear as two lines in the scatterplot of the sequence.
%H Rémy Sigrist, <a href="/A326776/b326776.txt">Table of n, a(n) for n = 1..10000</a>
%H Rémy Sigrist, <a href="/A326776/a326776.gp.txt">PARI program for A326776</a>
%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%e The first terms, alongside the divisors of A018252(n), are:
%e n a(n) div(A018252(n))
%e -- ---- ---------------
%e 1 1 (1)
%e 2 2 (1, 2, 4)
%e 3 3 (1, 2, 3, 6)
%e 4 4 (1, 2, 4, 8)
%e 5 9 (1, 3, 9)
%e 6 5 (1, 2, 5, 10)
%e 7 6 (1, 2, 3, 4, 6, 12)
%e 8 7 (1, 2, 7, 14)
%e 9 15 (1, 3, 5, 15)
%e 10 8 (1, 2, 4, 8, 16)
%o (PARI) See Links section.
%Y Cf. A018252, A093641, A111273.
%K nonn
%O 1,2
%A _Rémy Sigrist_, Jul 28 2019
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