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A119948
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Triangle of denominators of the square of a certain lower triangular matrix.
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3
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1, 4, 4, 18, 18, 9, 48, 48, 48, 16, 300, 300, 300, 100, 25, 120, 120, 120, 360, 180, 36, 980, 980, 980, 2940, 1470, 294, 49, 2240, 2240, 2240, 6720, 6720, 1344, 448, 64, 22680, 22680, 22680, 22680, 22680, 4536
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| The triangle of the corresponding numerators is A119947. The rationals appear in lowest terms.
The least common multiple (LCM) of row i gives [1, 4, 18, 48, 300, 360, 2940, 6720, 22680,...] which coincides with A081528.
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FORMULA
| a(i,j)= denominator(r(i,j)) with r(i,j):=(A^2)[i,j], where the matrix A has elements a[i,j] = 1/i if j=<i, 0 if j>i, (lower triangular).
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EXAMPLE
| [1];[4,4];[18,18,9];[48,48,48,16];[300,300,300,100,25];[120,120,120,360,180,36];...
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CROSSREFS
| Row sums give A119950. Row sums of the triangle of rationals give always 1.
Sequence in context: A116561 A086448 A128090 * A005222 A133039 A177117
Adjacent sequences: A119945 A119946 A119947 * A119949 A119950 A119951
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KEYWORD
| nonn,easy,frac,tabl
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AUTHOR
| Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), Jul 20 2006
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