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 A144216 C(m,2)+C(n,2), m>=1, n>=1: a rectangular array R read by antidiagonals. 2
 0, 1, 1, 3, 2, 3, 6, 4, 4, 6, 10, 7, 6, 7, 10, 15, 11, 9, 9, 11, 15, 21, 16, 13, 12, 13, 16, 21, 28, 22, 18, 16, 16, 18, 22, 28, 36, 29, 24, 21, 20, 21, 24, 29, 36, 45, 37, 31, 27, 25, 25, 27, 31, 37, 45, 55, 46, 39, 34, 31, 30, 31, 34, 39, 46, 55, 66, 56, 48, 42, 38, 36, 36, 38 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS R is the accumulation array (as defined at A144112) of the weight array A144217. As a triangular array read by rows (0; 1, 1; 3, 2, 3; 6, 4, 4, 6; ...), T(n,j) = (1/2)n(n+1-2j)+j(j-1) (1<=j<=n) is the sum of the distances from the vertex j of the path graph 1-2-...-n to all the other vertices. Example: T(4,2)=4 because in the path 1-2-3-4 the distances from vertex 2 to the vertices 1, 2, 3, 4 are 1, 0, 1, 2, respectively; 1+0+1+2=4. The sum of the terms in the upper left r X r submatrix is sum_{n=1..r} sum_{m=1..r} R(n,m) = A112742(r). - J. M. Bergot, Jun 18 2013 LINKS FORMULA R(m,n) = (m(m-1)+n(n-1))/2. EXAMPLE 0,  1,  3,  6, 10, 15, 21, 28, 36, 45, ...    1,  2,  4,  7, 11, 16, 22, 29, 37, 46, ...    3,  4,  6,  9, 13, 18, 24, 31, 39, 48, ...    6,  7,  9, 12, 16, 21, 27, 34, 42, 51, ...   10, 11, 13, 16, 20, 25, 31, 38, 46, 55, ...   15, 16, 18, 21, 25, 30, 36, 43, 51, 60, ...   21, 22, 24, 27, 31, 36, 42, 49, 57, 66, ...   28, 29, 31, 34, 38, 43, 49, 56, 64, 73, ...   36, 37, 39, 42, 46, 51, 57, 64, 72, 81, ...   45, 46, 48, 51, 55, 60, 66, 73, 81, 90, ... R(2,4) = binomial(2,2) + binomial(4,2) = 1 + 6 = 7. MAPLE T := proc (n, j) if j <= n then (1/2)*n*(n+1-2*j)+j*(j-1) else 0 end if end proc: for n to 12 do seq(T(n, j), j = 1 .. n) end do; # yields sequence in triangular form CROSSREFS Cf. A144217. Sequence in context: A266593 A130459 A323621 * A127938 A131990 A033771 Adjacent sequences:  A144213 A144214 A144215 * A144217 A144218 A144219 KEYWORD nonn,tabl AUTHOR Clark Kimberling, Sep 14 2008 STATUS approved

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Last modified May 14 16:10 EDT 2021. Contains 343884 sequences. (Running on oeis4.)