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A282511 Numerator of the sum of the reciprocals of the first n nonprimes. 9
1, 5, 17, 37, 119, 631, 661, 4807, 995, 2053, 703, 3599, 3679, 41309, 42079, 214091, 2829383, 25864847, 26250947, 26611307, 53898289, 54553489, 938220113, 135531719, 136990319, 2629070861, 2654652461, 2679594521, 18923442047, 19082164247, 19237359287 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..31.

EXAMPLE

The first few fractions are 1, 5/4, 17/12, 37/24, 119/72, 631/360, 661/360, 4807/2520, 995/504, 2053/

1008, 703/336, 3599/1680, ... - N. J. A. Sloane, Dec 15 2017

MATHEMATICA

With[{nn = 45}, Numerator@ Accumulate[1/Complement[Range@ nn, Prime@ Range@ PrimePi@ nn]]] (* Michael De Vlieger, Feb 18 2017 *)

PROG

(PARI) a018252(n) = if(n==1, 1, my(i=1); forcomposite(c=1, , i++; if(i==n, return(c))))

a(n) = numerator(sum(k=1, n, 1/a018252(k))) \\ Felix Fröhlich, Feb 17 2017

CROSSREFS

Cf. A018252 (nonprime numbers), A282512 (denominators).

The following fractions are all related to each other: Sum 1/n: A001008/A002805, Sum 1/prime(n): A024451/A002110 and A106830/A034386, Sum 1/nonprime(n): A282511/A282512, Sum 1/composite(n): A250133/A296358.

Sequence in context: A212876 A147219 A146280 * A147181 A146850 A146428

Adjacent sequences:  A282508 A282509 A282510 * A282512 A282513 A282514

KEYWORD

nonn,frac

AUTHOR

Ralf Steiner, Feb 17 2017

EXTENSIONS

More terms from Felix Fröhlich, Feb 17 2017

STATUS

approved

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Last modified February 21 07:18 EST 2018. Contains 299390 sequences. (Running on oeis4.)