A022449 c(p(n)) where p(k) is k-th prime including p(1)=1 and c(k) is k-th composite number.

4, 6, 8, 10, 14, 20, 22, 27, 30, 35, 44, 46, 54, 58, 62, 66, 75, 82, 85, 92, 96, 99, 108, 114, 120, 129, 134, 136, 142, 144, 148, 166, 171, 178, 182, 194, 196, 204, 210, 215, 221, 230, 232, 245, 247, 252, 254, 268, 285, 289, 291, 296, 302, 304, 318

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Comments

a(n) U A050435(n) = A002808(n), a(n+1) U A175251(n) = A002808(n) for n >= 1. a(n) = A065858(n-1) = composites (A002808) with prime (A000040) subscripts for n >=2. [From Jaroslav Krizek, Mar 13 2010]

Examples

			a(5) = 14 because a(5) = composite(noncomposite(5)) = composite(7) =14. _Jaroslav Krizek_, Mar 13 2010
		

References

• C. Kimberling, Fractal sequences and interspersions, Ars Combinatoria, vol. 45 p 157 1997.

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• C. Kimberling, Interspersions

Crossrefs

A065858 with a leading 4.

Programs

Haskell

a022449 = a002808 . a008578
a022449_list = map a002808 a008578_list
-- Reinhard Zumkeller, Jan 12 2013

Maple

A022449 := proc(n)
    A002808(A008578(n)) ;
end proc:
seq(A022449(n),n=1..40) ; # R. J. Mathar, Jan 28 2014

Mathematica

p[1] = 1; p[n_] := Prime[n - 1];
Composite[n_] := FixedPoint[n + PrimePi[#] + 1 & , n + PrimePi[n] + 1];
a[n_] := Composite[p[n]];
Array[a, 100] (* Jean-François Alcover, Jan 26 2018, after Robert G. Wilson v *)

Formula

a(n) = A002808(A008578(n)). - Jaroslav Krizek, Mar 13 2010

Extensions

Definition corrected by Christopher M. Tomaszewski (cmt1288(AT)comcast.net), Mar 30 2005