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 A118435 Triangle T, read by rows, equal to the matrix product T = H*[C^-1]*H, where H is the self-inverse triangle A118433 and C is Pascal's triangle. 9
 1, 1, 1, -3, 2, 1, -11, 15, 3, 1, 25, -44, -18, 4, 1, 41, -115, -110, 50, 5, 1, -43, 246, 375, -220, -45, 6, 1, 29, 315, 861, -805, -385, 105, 7, 1, -335, 232, -1204, 2296, 1750, -616, -84, 8, 1, -1199, 3033, 1044, 3780, 5166, -2898, -924, 180, 9, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS The matrix inverse of H*[C^-1]*H is H*C*H = A118438, where H^2 = I (identity). The matrix log, log(T) = A118441, is a matrix square root of a triangular matrix with a single diagonal (two rows down from the main diagonal). LINKS FORMULA Since T + T^-1 = C + C^-1, then [T^-1](n,k) = (1+(-1)^(n-k))*C(n,k) - T(n,k) is a formula for the matrix inverse T^-1 = A118438. EXAMPLE Triangle begins: 1; 1, 1; -3, 2, 1; -11, 15, 3, 1; 25,-44,-18, 4, 1; 41,-115,-110, 50, 5, 1; -43, 246, 375,-220,-45, 6, 1; 29, 315, 861,-805,-385, 105, 7, 1; -335, 232,-1204, 2296, 1750,-616,-84, 8, 1; -1199, 3033, 1044, 3780, 5166,-2898,-924, 180, 9, 1; ... The matrix log, log(T) = A118441, starts: 0; 1, 0; -4, 2, 0; -12, 12, 3, 0; 32,-48,-24, 4, 0; 80,-160,-120, 40, 5, 0; ... where matrix square, log(T)^2, is a single diagonal: 0; 0,0; 2,0,0; 0,6,0,0; 0,0,12,0,0; 0,0,0,20,0,0; ... PROG (PARI) {T(n, k)=local(M=matrix(n+1, n+1, r, c, if(r>=c, binomial(r-1, c-1)*(-1)^(r\2- (c-1)\2+r-c))), C=matrix(n+1, n+1, r, c, if(r>=c, binomial(r-1, c-1)))); (M*C^-1*M)[n+1, k+1]} CROSSREFS Cf. A118436 (column 0), A118437 (row sums), A118438 (matrix inverse), A118441 (matrix log), A118433 (self-inverse H). Sequence in context: A123513 A117442 A184182 * A115085 A110616 A059418 Adjacent sequences:  A118432 A118433 A118434 * A118436 A118437 A118438 KEYWORD sign,tabl AUTHOR Paul D. Hanna, Apr 28 2006 STATUS approved

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Last modified May 17 05:13 EDT 2021. Contains 343965 sequences. (Running on oeis4.)