OFFSET
0,2
COMMENTS
6851483347+21334239533=28185722880=2^28*3^1*5^1*7^1(31-almost prime).
hence a(31) <= 21334239533.
EXAMPLE
a(0)+a(1)=0+2=2 (prime = 1-almost prime)
a(1)+a(2)=2+2=4 (semiprime prime = 2-almost prime)
a(2)+a(3)=2+43=45=2*2*5 (3-almost prime)
a(29)+a(30)=6738061613+6851483347=13589544960=2^25*3^4*5^1 (30-almost prime).
MATHEMATICA
f[n_] := f[n] = Block[{p = f[n - 1], q = NextPrime[ f[n - 1] - 1]}, While[ PrimeOmega[p + q] != n, q = NextPrime@ q]; q]; f[0] = 0; Array[f, 22] (* Robert G. Wilson v, Jan 30 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Jan 30 2017
STATUS
approved