The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A131422 (A000012 * A127773) + (A127773 * A000012) - A000012. 1

%I

%S 1,3,5,6,8,11,10,12,15,19,15,17,20,24,29,21,23,26,30,35,41,28,30,33,

%T 37,42,48,55,36,38,41,45,50,56,63,71,45,47,50,54,59,65,72,80,89,55,57,

%U 60,64,69,75,82,90,99,109

%N (A000012 * A127773) + (A127773 * A000012) - A000012.

%C Left border = the triangular series, A000217. Right border = A028387, (1, 5, 11, 19, 29, 41, 55, 71, ...). Row sums = A131423: (1, 8, 25, 56, 105, 176, 273, ...).

%F (A000012 * A127773) + (A127773 * A000012) - A000012 as infinite lower triangular matrices.

%F T(n,k) = (n^2 + n + k^2 + k - 2)/2 (1 <= k <= n). - _Emeric Deutsch_, Sep 06 2008

%e First few rows of the triangle are:

%e 1;

%e 3, 5;

%e 6, 8, 11;

%e 10, 12, 15, 19;

%e 15, 17, 20, 24, 29;

%e 21, 23, 26, 30, 35, 41;

%e 28, 30, 33, 37, 42, 48, 55;

%e ...

%p T:=proc(n,k) options operator, arrow: (1/2)*n*(n+1)+(1/2)*k*(k+1)-1 end proc: for n to 10 do seq(T(n,k),k=1..n) end do; # yields sequence in triangular form - _Emeric Deutsch_, Sep 06 2008

%Y Cf. A127773, A000217, A028387, A131423.

%K nonn,tabl

%O 1,2

%A _Gary W. Adamson_, Jul 10 2007

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 22 14:14 EDT 2020. Contains 337291 sequences. (Running on oeis4.)