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A354418
a(n) is the denominator of the sum of the reciprocals of the first n squarefree numbers.
2
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
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
Sequence in context: A373350 A181812 A330648 * A074168 A079615 A076978
KEYWORD
nonn,frac
AUTHOR
Ilya Gutkovskiy, May 26 2022
STATUS
approved