This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A354418 #7 May 26 2022 09:52:51 %S A354418 1,2,6,30,5,35,70,770,10010,5005,15015,255255,4849845,1616615,3233230, %T A354418 74364290,37182145,1078282205,6469693230,200560490130,6077590610, %U A354418 3038795305,607759061,22487085257,44974170514,134922511542,5531822973222,921970495537,39644731308091 %N A354418 a(n) is the denominator of the sum of the reciprocals of the first n squarefree numbers. %e A354418 1, 3/2, 11/6, 61/30, 11/5, 82/35, 171/70, 1951/770, 26133/10010, 13424/5005, 41273/15015, ... %t A354418 Accumulate[1/Select[Range[43], SquareFreeQ]] // Denominator %o A354418 (PARI) a(n) = my(i=0, s=0); for(x=1, oo, if(core(x)==x, s+=1/x; i++; if(i==n, return(denominator(s))))) \\ _Felix Fröhlich_, May 26 2022 %Y A354418 Cf. A002110, A002805, A005117, A034386, A051451, A072983, A354417 (numerators). %K A354418 nonn,frac %O A354418 1,2 %A A354418 _Ilya Gutkovskiy_, May 26 2022