A305887 - OEIS

%I #13 Jun 18 2018 05:38:01

%S 4,5,10,29,173,249,19073,71489,1166789,3800333,7021253,15920129,

%T 84551600693

%N The least increasing sequence of numbers where all pairwise sums are semiprimes, with a(1)=4.

%C All terms > 10 are congruent to {3, 9} mod 10.

%C Triangle of resulting semiprimes begins:

%C     9

%C    14,  15

%C    33,  34,  39

%C   177, 178, 183, 202

%t Nest[Append[#, Block[{k = Last[#] + 1}, While[! AllTrue[#, PrimeOmega[k + #] == 2 &], k++]; k]] &, {4}, 7] (* _Michael De Vlieger_, Jun 14 2018 *)

%Y Cf. A001358, A116656, A164979, A181620.

%K nonn,more

%O 1,1

%A _Zak Seidov_, Jun 14 2018

%E a(13) from _Giovanni Resta_, Jun 14 2018