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 A141418 Triangle read by rows: T(n,k) = k * (2*n - k - 1) / 2, 1 <= k <= n. 4
 0, 1, 1, 2, 3, 3, 3, 5, 6, 6, 4, 7, 9, 10, 10, 5, 9, 12, 14, 15, 15, 6, 11, 15, 18, 20, 21, 21, 7, 13, 18, 22, 25, 27, 28, 28, 8, 15, 21, 26, 30, 33, 35, 36, 36, 9, 17, 24, 30, 35, 39, 42, 44, 45, 45 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS From Reinhard Zumkeller, Aug 04 2014: (Start) n-th row = half of Dynkin diagram weights for the Cartan Groups D_n. n-th row = partial sums of n-th row of A025581. (End) REFERENCES R. N. Cahn, Semi-Simple Lie Algebras and Their Representations, Dover, NY, 2006, ISBN 0-486-44999-8, p. 139. LINKS Reinhard Zumkeller, Rows n = 1..120 of triangle, flattened FORMULA T(n, K) = k*(2*n - k - 1)/2. Sum_{k=1..n} T(n, k) = 2*binomial(n+1, 3) = A007290(n+1). - Reinhard Zumkeller, Aug 04 2014 EXAMPLE Triangle begins as:   0;   1,  1;   2,  3,  3;   3,  5,  6,  6;   4,  7,  9, 10, 10;   5,  9, 12, 14, 15, 15;   6, 11, 15, 18, 20, 21, 21;   7, 13, 18, 22, 25, 27, 28, 28;   8, 15, 21, 26, 30, 33, 35, 36, 36;   9, 17, 24, 30, 35, 39, 42, 44, 45, 45; MAPLE A141418:= (n, k)-> k*(2*n-k-1)/2; seq(seq(A141418(n, k), k=1..n), n=1..12); # G. C. Greubel, Mar 30 2021 MATHEMATICA T[n_, k_]= k*(2*n-k-1)/2; Table[T[n, k], {n, 12}, {k, n}]//Flatten PROG (Haskell) a141418 n k = k * (2 * n - k - 1) `div` 2 a141418_row n = a141418_tabl !! (n-1) a141418_tabl = map (scanl1 (+)) a025581_tabl -- Reinhard Zumkeller, Aug 04 2014, Nov 18 2012 (Magma) [k*(2*n-k-1)/2: k in [1..n], n in [1..12]]; // G. C. Greubel, Mar 30 2021 (Sage) flatten([[k*(2*n-k-1)/2 for k in (1..n)] for n in (1..12)]) # G. C. Greubel, Mar 30 2021 CROSSREFS Cf. A025581, A087401, A141419. Sequence in context: A145281 A151687 A160573 * A287771 A335107 A130499 Adjacent sequences:  A141415 A141416 A141417 * A141419 A141420 A141421 KEYWORD nonn,tabl,easy AUTHOR Roger L. Bagula, Aug 05 2008 EXTENSIONS Edited by Reinhard Zumkeller, Nov 18 2012 STATUS approved

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Last modified June 13 18:45 EDT 2021. Contains 345008 sequences. (Running on oeis4.)