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

1,1

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]

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

Formula

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

Example

a(5) = 14 because a(5) = composite(noncomposite(5)) = composite(7) =14. Jaroslav Krizek, Mar 13 2010

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 *)

Prog

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

Crossrefs

A065858 with a leading 4.

Sequence in context: A328144 A327888 A103800 * A088686 A161344 A127792

Adjacent sequences: A022446 A022447 A022448 * A022450 A022451 A022452

Keyword

nonn

Author

Clark Kimberling

Extensions

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

Status

approved