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A166380
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Diagonal sums of exponential Riordan array [1+x^2*sec(x),x], A166378.
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1
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1, 3, 19, 223, 4667, 160045, 8207125, 587420875, 55869454855, 6809387511403, 1034264079708019, 191477762192490649, 42435372869814513769, 11090351278621719882899, 3374951549996881393302715
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = Sum_{k=0..n} C(n+k,2k)*A166377(k).
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MATHEMATICA
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(* The function RiordanArray is defined in A256893. *)
nmax = 14; R = RiordanArray[1 + #^2 Sec[#]&, #&, 2 nmax + 1, True];
a[n_] := Sum[R[[i, 2 n - i + 2]], {i, 2 n + 1, n + 1, -1}];
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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