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A216733 a(1)=1; thereafter a(n) = (n/2)*Sum_{i=1..n-1} K(i,n-i)*a(i)*a(n-i), where K(i,j)=i/j+j/i+2. 0
1, 4, 54, 1280, 44500, 2095632, 127881376, 9819500544, 928097190000, 106056995000000, 14432021983025504, 2308065337772034048, 428863163196474895616, 91656939861553564825600, 22332165732277725605760000, 6154560612828089005182025728, 1905106896258617768240402396928, 658221263587332244069472967367680, 252407458471654722567803941053452800 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..19.

P. L. Krapivsky and Colm Connaughton, Driven Brownian coagulation of polymers, arXiv preprint arXiv:1203.3905, 2012

MAPLE

K:=(i, j)->i/j+j/i+2;

B:=proc(n) option remember; global K;

if n=1 then 1 else

(n/2)*add( K(i, n-i)*B(i)*B(n-i), i=1..n-1); fi; end;

MATHEMATICA

K[i_, j_] := i/j + j/i + 2;

a[1] = 1; a[n_] := a[n] = (n/2) Sum[K[i, n-i] a[i] a[n-i], {i, 1, n-1}];

Array[a, 19] (* Jean-Fran├žois Alcover, Dec 06 2017 *)

CROSSREFS

Sequence in context: A259063 A138459 A111161 * A203039 A201731 A225823

Adjacent sequences:  A216730 A216731 A216732 * A216734 A216735 A216736

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Sep 17 2012

STATUS

approved

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Last modified December 15 20:00 EST 2019. Contains 330000 sequences. (Running on oeis4.)