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A131422 (A000012 * A127773) + (A127773 * A000012) - A000012. 1
1, 3, 5, 6, 8, 11, 10, 12, 15, 19, 15, 17, 20, 24, 29, 21, 23, 26, 30, 35, 41, 28, 30, 33, 37, 42, 48, 55, 36, 38, 41, 45, 50, 56, 63, 71, 45, 47, 50, 54, 59, 65, 72, 80, 89, 55, 57, 60, 64, 69, 75, 82, 90, 99, 109 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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, ...).

LINKS

Table of n, a(n) for n=1..55.

FORMULA

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

T(n,k) = (n^2 + n + k^2 + k - 2)/2 (1 <= k <= n). - Emeric Deutsch, Sep 06 2008

EXAMPLE

First few rows of the triangle are:

   1;

   3,  5;

   6,  8, 11;

  10, 12, 15, 19;

  15, 17, 20, 24, 29;

  21, 23, 26, 30, 35, 41;

  28, 30, 33, 37, 42, 48, 55;

  ...

MAPLE

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

CROSSREFS

Cf. A127773, A000217, A028387, A131423.

Sequence in context: A084810 A268896 A014254 * A301744 A087720 A309544

Adjacent sequences:  A131419 A131420 A131421 * A131423 A131424 A131425

KEYWORD

nonn,tabl

AUTHOR

Gary W. Adamson, Jul 10 2007

STATUS

approved

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Last modified August 10 16:56 EDT 2020. Contains 336381 sequences. (Running on oeis4.)