A074469 Subscript m such that SigmaComposite-Harmonic series cd[m]=Sum[1/A000203[A002808(k)],{k,1,m}]>=n.

32, 301, 2123, 13172, 76105, 420007, 2245009, 11719362, 60071831, 303487314, 1515211979

Offset

1,1

Links

Table of n, a(n) for n=1..11.

Mathematica

c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x] {s=0, s1=0}; Do[s=s+(1/DivisorSigma[1, c[n]]); If[Greater[Floor[s], s1], s1=Floor[s]; Print[{n, Floor[s]}]], {n, 1, 1000000}]

Prog

(PARI) a(n)=my(m, s=0.); for(c=4, (2*n+2)^(n+2), if(isprime(c), next, m++); s+=1/sigma(c); if(s>=n, return(m))) \\ Charles R Greathouse IV, Feb 19 2013

Crossrefs

Cf. A004080, A002387, A002808, A000203, A073255, A046024, A074631, A074633, A074468, A074470.

Sequence in context: A317228 A250563 A060158 * A159654 A061958 A050279

Adjacent sequences: A074466 A074467 A074468 * A074470 A074471 A074472

Keyword

hard,more,nonn

Author

Labos Elemer, Sep 05 2002

Extensions

a(6)-a(11) from Donovan Johnson, Aug 22 2011

Status

approved