

A216733


a(1)=1; thereafter a(n) = (n/2)*Sum_{i=1..n1} K(i,ni)*a(i)*a(ni), 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
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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, ni)*B(i)*B(ni), i=1..n1); fi; end;


MATHEMATICA

K[i_, j_] := i/j + j/i + 2;
a[1] = 1; a[n_] := a[n] = (n/2) Sum[K[i, ni] a[i] a[ni], {i, 1, n1}];
Array[a, 19] (* JeanFrançois 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



