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Search: id:A143685
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| 1, 1, 1, 1, 11, 1, 1, 21, 21, 1, 1, 31, 141, 31, 1, 1, 41, 361, 361, 41, 1, 1, 51, 681, 1991, 681, 51, 1, 1, 61, 1101, 5921, 5921, 1101, 61, 1, 1, 71, 1621, 13151, 29761, 13151, 1621, 71, 1, 1, 81, 2241, 24681, 96201
(list; table; graph; listen)
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OFFSET
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0,5
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FORMULA
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Number triangle T(n,k)=sum{j=0..n-k, binomial(n-k,j)binomial(k,j)10^j} Riordan array (1/(1-x),x(1+9x)/(1-x)). As a square array read by diagonals T(n, 0)=T(0, k)=1, T(n, k)=T(n, k-1)+9T(n-1, k-1)+T(n-1, k).
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CROSSREFS
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Cf. A143680, A143682.
Sequence in context: A010192 A105769 A157171 this_sequence A060270 A144440 A157209
Adjacent sequences: A143682 A143683 A143684 this_sequence A143686 A143687 A143688
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KEYWORD
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easy,nonn,tabl
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Aug 28 2008
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