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 A227506 Schroeder triangle sums: a(2*n-1) = A010683(2*n-2) and a(2*n) = A010683(2*n-1) - A001003(2*n-1). 2
 1, 1, 7, 17, 121, 353, 2591, 8257, 61921, 207905, 1582791, 5501073, 42344121, 150827073, 1170747519, 4247388417, 33186295681, 122125206977, 959260792775, 3570473750929, 28167068630713, 105820555054241, 837838806587167, 3172136074486337 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS The terms of this sequence equal the Fi1 sums, see A180662, of the Schroeder triangle A033877 (with offset 1 and n for columns and k for rows). LINKS FORMULA a(n) = Sum_{k=1..floor((n+1)/2)} A033877(2*k-1,n). a(2*n-1) = A010683(2*n-2) and a(2*n) = A010683(2*n-1) - A001003(2*n-1). G.f.: (1-4*x+x^2 - sqrt(1-6*x+x^2) + x*sqrt(1+6*x+x^2))/(8*x). MAPLE A227506 := proc(n) local k, T; T := proc(n, k) option remember; if n=1 then return(1) fi; if k

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Last modified October 29 12:00 EDT 2020. Contains 338066 sequences. (Running on oeis4.)