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%I #22 Nov 23 2019 09:37:51
%S 4,6,9,8,12,16,10,15,20,25,12,18,24,30,36,14,21,28,35,42,49,16,24,32,
%T 40,48,56,64,18,27,36,45,54,63,72,81,20,30,40,50,60,70,80,90,100,22,
%U 33,44,55,66,77,88,99,110,121,24,36,48,60,72,84,96,108,120
%N a(n) = (n+1) + (n+3/2)*H(n) - (H(n)^3)/2, where H(n)=A002024(n).
%C All terms are composite.
%H Blake Ralston, <a href="http://www.fq.math.ca/Scanned/23-2/ralston.pdf">Elemental Complete Composite Number Generators</a>, The Fibonacci Quarterly, Volume 23, Number 2, May 1985, pp. 149-150.
%F a(n) = (A002024(n)+1)*(n+1-A002024(n)*(A002024(n)-1)/2).
%F As a triangle: T(n, k) = (k + 1)*(n + 1) with 1 <= k <= n. - _Stefano Spezia_, Nov 23 2019
%e Sequence can be seen as a triangle that begins:
%e 4;
%e 6, 9;
%e 8, 12, 16;
%e 10, 15, 20, 25;
%e 12, 18, 24, 30, 36;
%e 14, 21, 28, 35, 42, 49;
%e 16, 24, 32, 40, 48, 56, 64;
%e ...
%t Table[(k+1)*(n+1),{n,1,11},{k,1,n}]//Flatten (* _Stefano Spezia_, Nov 23 2019 *)
%Y Cf. A002024.
%K nonn,tabl
%O 1,1
%A _Michel Marcus_, Oct 19 2012
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