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A329498
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Denominator of the rational number alpha_n involved in the calculation of the second moment of the n-th term of Ulam's "history-dependent random sequence".
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4
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1, 1, 2, 6, 24, 120, 720, 1680, 40320, 362880, 725760, 7983360, 2128896, 113218560, 387459072, 261534873600, 836911595520, 71137485619200, 75322043596800, 1621934672117760, 37429261664256000, 10218188434341888000, 224800145555521536000
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OFFSET
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1,3
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LINKS
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EXAMPLE
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0, 2, 21/2, 223/6, 2603/24, 33623/120, 477977/720, 2474153/1680, ...
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MAPLE
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s:=[1]; a:=[0];
for N from 2 to 40 do # N = n+1
n:=N-1;
t1:=s[n]+(1/n)*add(s[k], k=1..n)+2*s[n]/n+(2/n)*a[n];
t2:=s[n]+(1/n)*add(s[k], k=1..n)+a[n]+(2/n)*add(a[k], k=1..n);
s:=[op(s), t1];
a:=[op(a), t2];
od:
s; # sigma_n
a; # alpha_n
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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STATUS
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approved
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