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 A203994 Symmetric matrix based on f(i,j) = (i+j)*min{i,j}, by antidiagonals. 3
 1, 0, 0, -1, 1, -1, -2, 0, 0, -2, -3, -1, 1, -1, -3, -4, -2, 0, 0, -2, -4, -5, -3, -1, 1, -1, -3, -5, -6, -4, -2, 0, 0, -2, -4, -6, -7, -5, -3, -1, 1, -1, -3, -5, -7, -8, -6, -4, -2, 0, 0, -2, -4, -6, -8, -9, -7, -5, -3, -1, 1, -1, -3, -5, -7, -9 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,7 COMMENTS A203994 represents the matrix M given by f(i,j) = min(i-j+1,j-i+1) for i >= 1 and j >= 1. See A203995 for characteristic polynomials of principal submatrices of M, with interlacing zeros. LINKS G. C. Greubel, Antidiagonal rows n = 1..100, flattened EXAMPLE Northwest corner: 1 0 -1 -2 -3 0 1 0 -1 -2 -1 0 1 0 -1 2 -1 0 1 0 MATHEMATICA (* First program *) f[i_, j_] := Min[i - j + 1, j - i + 1]; m[n_] := Table[f[i, j], {i, 1, n}, {j, 1, n}] TableForm[m[6]] (* 6 X 6 principal submatrix *) Flatten[Table[f[i, n + 1 - i], {n, 1, 12}, {i, 1, n}]] (* A203994 *) p[n_] := CharacteristicPolynomial[m[n], x]; c[n_] := CoefficientList[p[n], x] TableForm[Flatten[Table[p[n], {n, 1, 10}]]] Table[c[n], {n, 1, 12}] Flatten[%] (* A203995 *) TableForm[Table[c[n], {n, 1, 10}]] (* Second program *) Table[Min[2*k-n, n-2*k+2], {n, 15}, {k, n}]//Flatten (* G. C. Greubel, Jul 23 2019 *) PROG (PARI) for(n=1, 15, for(k=1, n, print1(min(2*k-n, n-2*k+2), ", "))) \\ G. C. Greubel, Jul 23 2019 (Magma) [Min(2*k-n, n-2*k+2): k in [1..n], n in [1..15]]; // G. C. Greubel, Jul 23 2019 (Sage) [[min(2*k-n, n-2*k+2) for k in (1..n)] for n in (1..15)] # G. C. Greubel, Jul 23 2019 (GAP) Flat(List([1..15], n-> List([1..n], k-> Minimum(2*k-n, n-2*k+2) ))); # G. C. Greubel, Jul 23 2019 CROSSREFS Cf. A203995, A202453. Sequence in context: A280542 A340378 A274575 * A285725 A215889 A195022 Adjacent sequences: A203991 A203992 A203993 * A203995 A203996 A203997 KEYWORD tabl,sign AUTHOR Clark Kimberling, Jan 09 2012 STATUS approved

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Last modified June 19 15:41 EDT 2024. Contains 373503 sequences. (Running on oeis4.)