OFFSET
1,10
LINKS
Robert Israel, Table of n, a(n) for n = 1..5000
EXAMPLE
a(10) = 2 because 20 = 5+15 = 11+9 where 5 and 11 are primes and 15 and 9 are semiprimes.
MAPLE
N:= 300: # for a(1)..a(N/2)
P:= select(isprime, [seq(i, i=3..N, 2)]):
S:= sort(select(`<`, [seq(seq(P[i]*P[j], i=1..j), j=1..nops(P))], N)):
V:= Vector(N):
for p in P do
for s in S do
v:= p+s;
if v>N then break fi;
V[v]:= V[v]+1
od od:
seq(V[i], i=2..N, 2);
MATHEMATICA
{0}~Join~Array[Count[IntegerPartitions[2 #, {2}, All, -(# - 2)], _?(And[AnyTrue[#, PrimeQ], AnyTrue[#, PrimeOmega[#] == 2 &]] &)] &, 86, 2] (* Michael De Vlieger, Dec 13 2020 *)
PROG
(PARI) a(n) = {my(nb=0); forprime(p=3, 2*n, if (bigomega(2*n-p) == 2, nb++); ); nb; } \\ Michel Marcus, Dec 14 2020
CROSSREFS
KEYWORD
nonn,look
AUTHOR
J. M. Bergot and Robert Israel, Dec 13 2020
STATUS
approved