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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

Table of n, a(n) for n=0..27.

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.)