A089733 Begin with 1; add a distinct prime to get a composite number, then add a distinct composite number to get a prime; repeat.

1, 4, 13, 15, 19, 24, 59, 66, 131, 142, 157, 170, 191, 208, 233, 252, 307, 330, 379, 408, 499, 530, 557, 594, 709, 750, 827, 870, 991, 1038, 1123, 1176, 1301, 1360, 1399, 1460, 1493, 1560, 1693, 1764, 1907, 1980, 2099, 2178, 2273, 2356, 2437, 2526, 2671, 2768

Offset

1,2

Comments

a(2n) - a(2n-1) = prime(n) for n > 2.

Links

Table of n, a(n) for n=1..50.

Maple

p:=[]:c:=[]:a:=[1]:for n from 2 to 60 do for i from 2 do m:=a[n-1]+i: if n mod 2=0 then if isprime(i) and not isprime(m) and not member(i, p) then p:=[op(p), i]: a:=[op(a), m]: break fi else if isprime(m) and not isprime(i) and not member(i, c) then c:=[op(c), i]: a:=[op(a), m]: break fi fi od od: op(a); # C. Ronaldo

Crossrefs

Sequence in context: A014563 A066774 A075339 * A126908 A106681 A144947

Adjacent sequences: A089730 A089731 A089732 * A089734 A089735 A089736

Keyword

base,nonn

Author

Amarnath Murthy, Nov 19 2003

Extensions

More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 26 2004

Status

approved