A175251 Composites (A002808) with nonprime (A018252) subscripts.

4, 9, 12, 15, 16, 18, 21, 24, 25, 26, 28, 32, 33, 34, 36, 38, 39, 40, 42, 45, 48, 49, 50, 51, 52, 55, 56, 57, 60, 63, 64, 65, 68, 69, 70, 72, 74, 76, 77, 78, 80, 81, 84, 86, 87, 88, 90, 91, 93, 94, 95, 98, 100

Offset

1,1

Comments

a(n) = composite(nonprime(n)) = A002808(A018252(n)). a(n) U A065858(n) = A002808(n), a(n+1) U A022449(n) = A002808(n) for n >= 1. a(1) = 4, a(n) = A050435(n-1) = composites (A002808) with composite (A002808) subscripts for n >=2.

Links

Table of n, a(n) for n=1..53.

Example

a(5) = 16 because a(5) = c(b(5)) = c(9) = 16, c = composite, b = nonprime.

Crossrefs

Sequence in context: A312849 A161544 A179395 * A368998 A287367 A312850

Adjacent sequences: A175248 A175249 A175250 * A175252 A175253 A175254

Keyword

nonn

Author

Jaroslav Krizek, Mar 13 2010

Status

approved