A282503 Denominator of Sum_{i = 1..n} (if(isprime(i), 0, 1/i)).

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

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