A354418 a(n) is the denominator of the sum of the reciprocals of the first n squarefree numbers.

1, 2, 6, 30, 5, 35, 70, 770, 10010, 5005, 15015, 255255, 4849845, 1616615, 3233230, 74364290, 37182145, 1078282205, 6469693230, 200560490130, 6077590610, 3038795305, 607759061, 22487085257, 44974170514, 134922511542, 5531822973222, 921970495537, 39644731308091

Offset

1,2

Links

Table of n, a(n) for n=1..29.

Example

1, 3/2, 11/6, 61/30, 11/5, 82/35, 171/70, 1951/770, 26133/10010, 13424/5005, 41273/15015, ...

Mathematica

Accumulate[1/Select[Range[43], SquareFreeQ]] // Denominator

Prog

(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

Crossrefs

Cf. A002110, A002805, A005117, A034386, A051451, A072983, A354417 (numerators).

Sequence in context: A373350 A181812 A330648 * A074168 A079615 A076978

Adjacent sequences: A354415 A354416 A354417 * A354419 A354420 A354421

Keyword

nonn,frac

Author

Ilya Gutkovskiy, May 26 2022

Status

approved