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 A122177 Triangle, read by rows, where T(n,k) = C( k*(k+1)/2 + n-k + 2, n-k) for n>=k>=0. 5
 1, 3, 1, 6, 4, 1, 10, 10, 6, 1, 15, 20, 21, 9, 1, 21, 35, 56, 45, 13, 1, 28, 56, 126, 165, 91, 18, 1, 36, 84, 252, 495, 455, 171, 24, 1, 45, 120, 462, 1287, 1820, 1140, 300, 31, 1, 55, 165, 792, 3003, 6188, 5985, 2600, 496, 39, 1, 66, 220, 1287, 6435, 18564, 26334 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Remarkably, column k of the matrix inverse (A121437) equals signed column k of matrix power: A107876^(k*(k+1)/2 + 3) for k>=0. LINKS EXAMPLE Triangle begins: 1; 3, 1; 6, 4, 1; 10, 10, 6, 1; 15, 20, 21, 9, 1; 21, 35, 56, 45, 13, 1; 28, 56, 126, 165, 91, 18, 1; 36, 84, 252, 495, 455, 171, 24, 1; 45, 120, 462, 1287, 1820, 1140, 300, 31, 1; ... PROG (PARI) T(n, k)=if(n

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Last modified May 14 16:48 EDT 2021. Contains 343898 sequences. (Running on oeis4.)