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Search: id:A090220
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| 1, 1, 1, 1, 2, 10, 20, 70, 560, 1680, 2800, 30800, 369600, 800800, 11211200, 168168000, 448448000, 7623616000, 137225088000, 434546112000, 8690922240000, 182509367040000, 669201012480000, 15391623287040000, 369398958888960000
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OFFSET
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1,5
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COMMENT
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The corresponding numerator sequence is N(n) := [1, 6, 3, 1, 3, 3, 1, 3, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1] for n=1..26.
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FORMULA
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a(n)= LCM(seq(denominator(a(n+2, m))), m=1..n)), with the a(n, m) formula of A090219(n, m) but without the 1/b(n-2) factor, and LMC denotes the least common multiple of a set of numbers.
N(n) := GCD(seq(numerator(a(n+2, m))), m=1..n)), with the a(n, m) formula of A090219(n, m) but without the 1/b(n-2) factor, and GCD denotes the greatest common divisor>1 of a set of numbers.
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EXAMPLE
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The fifth (k=7) column of A078741 needs in A090219 the factor b(5) := N(5)/a(5)= 3/2.
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CROSSREFS
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Sequence in context: A038103 A139592 A120552 this_sequence A029994 A004643 A037422
Adjacent sequences: A090217 A090218 A090219 this_sequence A090221 A090222 A090223
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KEYWORD
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nonn,easy
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AUTHOR
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Wolfdieter Lang (wolfdieter.lang_AT_physik_DOT_uni-karlsruhe_DOT_de), Dec 01 2003
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