A166983 The n-th composite minus the number of its divisors.

1, 2, 4, 6, 6, 6, 10, 11, 11, 12, 14, 17, 18, 16, 22, 22, 23, 22, 22, 26, 29, 30, 31, 27, 34, 35, 32, 34, 38, 39, 42, 38, 46, 44, 47, 46, 46, 51, 48, 53, 54, 48, 58, 57, 57, 61, 58, 62, 65, 62, 60, 70, 69, 70, 73, 70, 70, 76, 78, 72, 81, 82, 83, 80, 78, 87, 86, 89, 90, 91, 84

Offset

1,2

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n)=A002808(n)-A000005(A002808(n)) = A002808(n)-A035004(n+1).

Example

a(1)=4-3=1, a(2)=6-4=2, a(3)=8-4=4.

Mathematica

With[{comps=Rest[Complement[Range[100], Prime[Range[PrimePi[100]]]]]}, #-DivisorSigma[0, #]&/@comps] (* Harvey P. Dale, Dec 16 2011 *)
#-DivisorSigma[0, #]&/@Select[Range[100], CompositeQ] (* Harvey P. Dale, Aug 20 2025 *)

Crossrefs

Cf. A000005, A002808.

Sequence in context: A050825 A174342 A111150 * A361689 A078611 A211376

Adjacent sequences: A166980 A166981 A166982 * A166984 A166985 A166986

Keyword

nonn

Author

Juri-Stepan Gerasimov, Oct 26 2009

Extensions

Formula and two entries corrected by R. J. Mathar, May 21 2010.

Status

approved