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Search: id:A109154
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| 1, 2, 4, 14, 56, 262, 1348, 7574, 45616, 292442, 1978788, 14060654, 104403304, 807162070, 6476169012, 53781863598, 461194543136, 4075567775538, 37048022605956, 345883045698222, 3311798037556952, 32480125869403430
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OFFSET
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0,2
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COMMENT
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Triangular matrix T=A109152 satisfies: T(n,k) = [T^2](n-1,k) for n>k+1>=1, with T(n,n) = 1 and T(n+1,n) = n+1 for n>=0.
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PROGRAM
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(PARI) {a(n)=local(M=matrix(n+2, n+2)); M=M^0; for(i=1, n, M=matrix(n+2, n+2, r, c, if(r>=c, if(r==c, 1, if(r==c+1, c, (M^2)[r-1, c]))))); return(M[n+2, 2])}
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CROSSREFS
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Cf. A109152 (triangle), A109153 (column 0), A109155 (column 2), A109156 (row sums).
Adjacent sequences: A109151 A109152 A109153 this_sequence A109155 A109156 A109157
Sequence in context: A131180 A047990 A000939 this_sequence A030853 A030962 A030830
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), Jun 20 2005
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