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A120499 Irregular triangle read by rows in which the n-th row consists of the positive integers which are <= n and divisible by exactly one prime dividing n (but are coprime to every other prime dividing n). (a(1) = 1).

%I A120499 #12 Oct 01 2017 00:02:29
%S A120499 1,2,3,2,4,5,2,3,4,7,2,4,6,8,3,6,9,2,4,5,6,8,11,2,3,4,8,9,10,13,2,4,6,
%T A120499 7,8,10,12,3,5,6,9,10,12,2,4,6,8,10,12,14,16,17,2,3,4,8,9,10,14,15,16,
%U A120499 19,2,4,5,6,8,12,14,15,16,18,3,6,7,9,12,14,15,18,2,4,6,8,10,11,12,14,16,18
%N A120499 Irregular triangle read by rows in which the n-th row consists of the positive integers which are <= n and divisible by exactly one prime dividing n (but are coprime to every other prime dividing n). (a(1) = 1).
%C A120499 n-th row of array has A116512(n) terms.
%H A120499 Michael De Vlieger, <a href="/A120499/b120499.txt">Table of n, a(n) for n = 1..10589</a> (rows 1 <= n <= 250)
%e A120499 12 is divisible by the primes 2 and 3. 2,3,4,8,9,10 are those positive integers which are <= 12, which are divisible by 2 or 3, but are not divisible by 2 and 3. So the 12th row of the array is {2,3,4,8,9,10}.
%t A120499 Table[Select[Range@ n, Function[k, Total@ Boole@ Map[Divisible[k, #] &, FactorInteger[n][[All, 1]]] == 1]], {n, 22}] // Flatten (* _Michael De Vlieger_, Sep 30 2017 *)
%Y A120499 Cf. A116512, A119790, A119794.
%K A120499 nonn,tabf
%O A120499 1,2
%A A120499 _Leroy Quet_, Aug 06 2006
%E A120499 Corrected by _Ray Chandler_, Aug 29 2006