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A187116
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A diagonal of triangle A187115.
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4
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1, 4, 20, 138, 1258, 14476, 202655, 3354848, 64246776, 1398909332, 34157026526, 924757926320, 27503093599024, 891534666547216, 31289986924954924, 1182213869836721036, 47846600590876178320, 2065282617724684345208
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OFFSET
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2,2
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COMMENTS
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Definition of triangle: A187115(n,k) = [y^k] R_{n-1}(y+y^2) for k=2..n, n>2, where R_n(y) is the n-th row polynomial with R_2(y)=y^2.
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LINKS
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FORMULA
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Equals column 1 in the matrix square of triangle A135080.
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PROG
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(PARI) {a(n)=local(Rn=y^2); for(m=2, n+1, Rn=subst(truncate(Rn), y, y+y^2+O(y^m))); polcoeff(Rn, n, y)}
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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