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%I #22 Feb 03 2019 18:08:07
%S 4,6,10,9,14,15,22,21,25,34,33,39,46,46,49,55,62,74,69,74,86,82,85,91,
%T 134,106,106,118,111,115,129,133,142,141,166,158,159,166,169,178,202,
%U 183,194,206,202,201,213,226,274,302,235,262,254,253,259,265,274,274,314,298,302
%N a(n) = smallest semiprime such that prime(n) = a(n) - p, p prime.
%e a(1) = 4 because prime(1) = 4 - 2;
%e a(2) = 6 because prime(2) = 6 - 3;
%e a(3) = 10 because prime(3) = 10 - 5;
%e a(4) = 9 because prime(4) = 9 - 2;
%e a(5) = 14 because prime(5) = 14 - 3.
%p isA001358 := proc(n) return(numtheory[bigomega](n) = 2) ; end proc:
%p A188673 := proc(n) local p,j ; p := ithprime(n) ; for j from 1 do if isA001358(p+ithprime(j)) then return p+ithprime(j) ; end if; end do; end proc: # _R. J. Mathar_, Apr 16 2011
%Y Cf. A000040, A001358.
%K nonn
%O 1,1
%A _Michel Lagneau_, Apr 14 2011