A153803 a(n) = A153800(n) - A000043(n).

0, 0, 0, 0, 0, 2, 6, 10, 49, 103, 122, 167

Offset: 1

Author

Omar E. Pol, Jan 13 2009

Keywords

• more
• nonn

Crossrefs

Cf. A000040, A000043, A000668, A000225, A000396, A007691, A153800, A153801, A153802.

Programs

Mathematica

a007691[m_] := Block[{f = 0, i = 1}, While[f < m, If[Divisible[DivisorSigma[1, i], i], ++f]; ++i;]; Return[i - 1]]
a153800[n_] := Block[{i = 2, j, f = 0}, While[f < n, j = a007691[i]; If[PerfectNumberQ[j], ++f;]; ++i]; Return[i - 1]]
a[n_] := a153800[n] - MersennePrimeExponent[n]
a /@ Range[1, 4] (* Julien Kluge, Dec 15 2016 *)