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 A282503 Denominator of Sum_{i = 1..n} (if(isprime(i), 0, 1/i)). 2
 1, 1, 1, 4, 4, 12, 12, 24, 72, 360, 360, 360, 360, 2520, 504, 1008, 1008, 336, 336, 1680, 1680, 18480, 18480, 18480, 92400, 1201200, 10810800, 10810800, 10810800, 10810800, 10810800, 21621600, 21621600, 367567200, 52509600, 52509600, 52509600, 997682400, 997682400 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 LINKS Robert Israel, Table of n, a(n) for n = 1..4573 EXAMPLE See examples in A282501. MAPLE S:= 0: for n from 1 to 100 do   if not isprime(n) then S:= S+1/n fi;   A[n]:= denom(S); od: seq(A[i], i=1..100); # Robert Israel, Feb 21 2017 MATHEMATICA a[n_]=Sum[If[Element[k, Primes], 0, 1/k], {k, 1, n}]; Denominator /@ a /@ Range[1, 10] PROG (PARI) lista(nn) = {sr = 0; for (n=1, nn, if (!isprime(n), sr += 1/n); print1(denominator(sr), ", "); ); } \\ Michel Marcus, Feb 18 2017 CROSSREFS Cf. A018252 (nonprime numbers), A282501 (numerators). Sequence in context: A168398 A281913 A178776 * A323189 A121189 A136485 Adjacent sequences:  A282500 A282501 A282502 * A282504 A282505 A282506 KEYWORD nonn,frac AUTHOR Ralf Steiner, Feb 16 2017 EXTENSIONS More terms from Michel Marcus, Feb 18 2017 STATUS approved

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Last modified January 18 07:36 EST 2019. Contains 319269 sequences. (Running on oeis4.)