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 A280788 Convolution of A000081 and A027852, shifted by 3 leading zeros. 4
 1, 2, 6, 15, 41, 106, 284, 750, 2010, 5382, 14523, 39290, 106854, 291552, 798675, 2194828, 6051153, 16730373, 46383002, 128910484, 359115067, 1002575810, 2804667061, 7860780578, 22070885735, 62071872704, 174842835886, 493217417610 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS R. J. Mathar, Topologically Distinct Sets of Non-intersecting Circles in the Plane, arXiv:1603.00077 [math.CO], 2016. See (71). MAPLE A280788 := proc(N::integer) if N = 0 then 1; else add(A000081(Nprime+1)*A027852(N-Nprime+2), Nprime=0..N) ; end if; end proc: seq(A280788(n), n=0..30) ; # R. J. Mathar, Mar 06 2017 MATHEMATICA a81[n_] := a81[n] = If[n <= 1, n, Sum[a81[n - j]*DivisorSum[j, #*a81[#]&], {j, n - 1}]/(n - 1)]; A027852[n_] := Module[{dh = 0, np}, For[np = 0, np <= n, np++, dh = a81[np] * a81[n - np] + dh]; If[EvenQ[n], dh = a81[n/2] + dh]; dh/2]; A280788[n_] := If[n == 0, 1, Sum[a81[np+1]*A027852[n-np+2], {np, 0, n}]]; Table[A280788[n], {n, 0, 27}] (* Jean-François Alcover, Nov 23 2017, from Maple *) CROSSREFS Cf. A269800, A280786, A280787, A027852. Sequence in context: A074446 A303551 A180666 * A121328 A348012 A139379 Adjacent sequences: A280785 A280786 A280787 * A280789 A280790 A280791 KEYWORD nonn AUTHOR N. J. A. Sloane, Jan 20 2017 STATUS approved

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Last modified February 3 13:54 EST 2023. Contains 360035 sequences. (Running on oeis4.)