A138561 Start with the list {1}; for each n >= 1, append p(n) primes followed by c(n) composite numbers, where p(n) is the n-th prime and c(n) is the n-th composite number.

1, 2, 3, 4, 6, 8, 9, 5, 7, 11, 10, 12, 14, 15, 16, 18, 13, 17, 19, 23, 29, 20, 21, 22, 24, 25, 26, 27, 28, 31, 37, 41, 43, 47, 53, 59, 30, 32, 33, 34, 35, 36, 38, 39, 40, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 109, 113, 127, 131

Offset

1,2

Comments

A rearrangement of the natural numbers.

Links

Table of n, a(n) for n=1..70.

Example

We start with 1; p(1) = 2 is the first prime and the next two terms are 2,3 while c(1)=4 is the first composite number and the next four terms are 4,6,8,9 and so on.

Crossrefs

Sequence in context: A176798 A067118 A320503 * A376198 A333841 A231236

Adjacent sequences: A138558 A138559 A138560 * A138562 A138563 A138564

Keyword

easy,nonn

Author

Amarnath Murthy, Mar 25 2008

Extensions

More terms from Sean A. Irvine, Apr 13 2010

Status

approved