%I #4 Aug 27 2019 10:42:02
%S 1,1,2,3,3,3,3,4,4,4,5,5,5,5,5,5,6,6,6,6,6,7,7,7,7,7,7,7,7,8,8,8,8,8,
%T 8,8,9,9,9,9,9,9,9,9,9,9,10,10,10,10,10,10,10,10,10,11,11,11,11,11,11,
%U 11,11,11,11,11,11,12,12,12,12,12,12,12,12,12,12,12
%N Two 1's, one 2, four 3's, three 4's ...
%t {Table[#[[1]],#[[2]]],Table[#[[2]],#[[1]]]}&/@Partition[Range[20],2]// Flatten (* _Harvey P. Dale_, Aug 27 2019 *)
%K nonn
%O 1,3
%A _Paul Curtz_, Jul 17 2007