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A161205 Triangle read by rows in which row n lists 2n-1 followed by 2n numbers 2n.

%I A161205 #17 Jun 07 2019 20:32:01
%S A161205 1,2,2,3,4,4,4,4,5,6,6,6,6,6,6,7,8,8,8,8,8,8,8,8,9,10,10,10,10,10,10,
%T A161205 10,10,10,10,11,12,12,12,12,12,12,12,12,12,12,12,12,13,14,14,14,14,14,
%U A161205 14,14,14,14,14,14,14,14,14,15,16,16,16,16,16,16,16,16
%N A161205 Triangle read by rows in which row n lists 2n-1 followed by 2n numbers 2n.
%C A161205 Row sums: A125202(n+1). - _R. J. Mathar_, Feb 16 2010
%H A161205 Omar E. Pol, <a href="http://www.polprimos.com">Determinacion geometrica de los numeros primos y perfectos</a>
%H A161205 Omar E. Pol, <a href="http://www.polprimos.com/imagenespub/polprdipi.jpg">Illustration: Divisors and pi(x)</a>
%F A161205 If n is a perfect square, then a(n) = 2*sqrt(n)-1; otherwise a(n) = 2*floor(sqrt(n)). - _Nathaniel Johnston_, May 06 2011
%F A161205 a(n) = A000196(n-1) + A000196(n) = floor(sqrt(n-1)) + floor(sqrt(n)). - _Ridouane Oudra_, Jun 07 2019
%e A161205 Triangle begins:
%e A161205   1,  2,  2;
%e A161205   3,  4,  4,  4,  4;
%e A161205   5,  6,  6,  6,  6,  6,  6;
%e A161205   7,  8,  8,  8,  8,  8,  8,  8,  8;
%e A161205   9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10;
%p A161205 A161205 := proc(n,k) if k=1 then 2*n-1; else 2*n; end if; end proc: seq(seq(A161205(n,k),k=1..2*n+1),n=1..12) ; # _R. J. Mathar_, Feb 16 2010
%Y A161205 Cf. A000005, A000720, A018253, A125202, A160811, A160812, A161339.
%K A161205 easy,nonn,tabf
%O A161205 1,2
%A A161205 _Omar E. Pol_, Jun 19 2009
%E A161205 More terms from _R. J. Mathar_, Feb 16 2010