A375534 - OEIS

%I #20 Oct 21 2024 11:43:14

%S 1,2,6,30,210,4830,140070,5182590,222851370,10474014390,555122762670,

%T 32752242997530,2194400280834510,160191220500919230,

%U 12655106419572619170,1050373832824527391110,93483271121382937808790,9067877298774144967452630,2022136637626634327741936490

%N a(n) = denominator of Sum_{i=1..n} 1/A038603(i). 	

%C See A375533 (the numerators) for further information.

%H Alois P. Heinz, <a href="/A375534/b375534.txt">Table of n, a(n) for n = 0..313</a>

%H N. J. A. Sloane, <a href="https://www.youtube.com/watch?v=3RAYoaKMckM">A Nasty Surprise in a Sequence and Other OEIS Stories</a>, Experimental Mathematics Seminar, Rutgers University, Oct 10 2024, Youtube video; <a href="https://sites.math.rutgers.edu/~zeilberg/expmath/sloane85BD.pdf">Slides</a> [Mentions this sequence]

%e The first few sums are 0/1, 1/2, 5/6, 31/30, 247/210, 5891/4830, 175669/140070, 6639823/5182590,  ...

%t a[n_]:=Denominator[Sum[ 1/Part[ResourceFunction["OEISSequence"]["A038603"],i],{i,n}]]; Array[a,18] (* _Stefano Spezia_, Sep 06 2024 *)

%Y Cf. A002110, A038603, A375533, A375805.

%K nonn,frac

%O 0,2

%A _N. J. A. Sloane_, Sep 06 2024

%E a(0)=1 prepended by _Alois P. Heinz_, Oct 21 2024