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 A166380 Diagonal sums of exponential Riordan array [1+x^2*sec(x),x], A166378. 1
 1, 3, 19, 223, 4667, 160045, 8207125, 587420875, 55869454855, 6809387511403, 1034264079708019, 191477762192490649, 42435372869814513769, 11090351278621719882899, 3374951549996881393302715 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS FORMULA a(n) = Sum_{k=0..n} C(n+k,2k)*A166377(k). MATHEMATICA (* 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}]; Table[a[n], {n, 0, nmax}] (* Jean-François Alcover, Jul 20 2019 *) CROSSREFS Cf. A166377, A166378. Sequence in context: A277407 A271587 A217906 * A136652 A136504 A003111 Adjacent sequences:  A166377 A166378 A166379 * A166381 A166382 A166383 KEYWORD easy,nonn AUTHOR Paul Barry, Oct 13 2009 STATUS approved

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Last modified December 5 17:42 EST 2019. Contains 329768 sequences. (Running on oeis4.)