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 A076770 Even numbers representable as the sum of two odd composites. 2

%I #10 Mar 31 2019 04:02:06

%S 18,24,30,34,36,40,42,44,46,48,50,52,54,56,58,60,62,64,66,68,70,72,74,

%T 76,78,80,82,84,86,88,90,92,94,96,98,100,102,104,106,108,110,112,114,

%U 116,118,120,122,124,126,128,130,132,134,136,138,140,142,144,146,148

%N Even numbers representable as the sum of two odd composites.

%C 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]

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

%o (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)))

%Y Cf. A118081.

%K nonn

%O 1,1

%A _Jon Perry_, Nov 14 2002

%E Corrected by _Don Reble_, Nov 20 2006

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Last modified September 26 04:29 EDT 2023. Contains 365653 sequences. (Running on oeis4.)