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Denominator of Sum_{k=0..n} 1/binomial(n,k).
5

%I #17 Feb 21 2022 01:16:53

%S 1,1,2,3,3,5,60,105,35,63,630,1155,6930,12870,24024,9009,9009,17017,

%T 306306,2909907,692835,1322685,58198140,111546435,66927861,128707425,

%U 371821450,717084225,20078358300,38818159380,2329089562800,4512611027925

%N Denominator of Sum_{k=0..n} 1/binomial(n,k).

%D See A046825, which is the main entry.

%H T. D. Noe, <a href="/A046826/b046826.txt">Table of n, a(n) for n=0..200</a>

%F a(n) = denominator( A003149(n)/n! ). - _G. C. Greubel_, May 24 2021

%e 1, 2, 5/2, 8/3, 8/3, 13/5, 151/60, 256/105, 83/35, 146/63, 1433/630, 2588/1155, 15341/6930, 28211/12870, 52235/24024, 19456/9009, 19345/9009, ... = A046825/A046826

%t Denominator[Table[Sum[1/Binomial[n,k],{k,0,n}],{n,0,40}]] (* _Harvey P. Dale_, Nov 05 2011 *)

%o (Magma) [Denominator((&+[1/Binomial(n,j): j in [0..n]])): n in [0..40]]; // _G. C. Greubel_, May 24 2021

%o (Sage) [denominator(sum(1/binomial(n,j) for j in (0..n))) for n in (0..40)] # _G. C. Greubel_, May 24 2021

%Y Cf. A003149, A046825.

%K nonn,easy,frac,nice

%O 0,3

%A _N. J. A. Sloane_