A076770 Even numbers representable as the sum of two odd composites.

18, 24, 30, 34, 36, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148

Offset

1,1

Comments

If n is even and n > 38, at least one of (n-15), (n-25), (n-35) is an odd number divisible by 3 and greater than 3. So every even number > 38 is a term. [Jack Brennen]

Links

Table of n, a(n) for n=1..60.

Example

40 can be represented as 15+25 where 15 and 25 are both composite numbers, so 40 is a term.

Prog

(PARI) v=vector(5000); vc=1; forstep (n=9, 300, 2, if (isprime(n), continue, forstep (j=9, 300, 2, if (isprime(j), continue, x=n+j; fl=true; for (i=1, vc, if (v[i]==x, fl=false; break)); if (fl==true, v[vc]=x; vc++))))); print(vc); v=vecsort(vecextract(v, concat("1..", vc-1)))

Crossrefs

Cf. A118081.

Sequence in context: A086473 A271327 A243539 * A105679 A160810 A376384

Adjacent sequences: A076767 A076768 A076769 * A076771 A076772 A076773

Keyword

nonn

Author

Jon Perry, Nov 14 2002

Extensions

Corrected by Don Reble, Nov 20 2006

Status

approved