%I A117406
%S A117406 3,2,0,1,2,1,1,1,1,2,1,3,1,1,1,2,3,5,1,2,1,1
%V A117406 3,2,0,1,-2,1,1,1,1,-2,-1,3,-1,1,1,-2,-3,-5,1,-2,1,1
%N A117406 Integer k such that 2^n + k = A117405(n).
%C A117406 After n=2, never again is a(n) = 0. Semiprime analogue of A117388 Integer 
               k such that 2^n + k = A117387(n). A117387(n) is prime nearest to 
               2^n. (In case of a tie, choose the smaller).
%F A117406 a(n) = A117405(n) - 2^n. a(n) = Min{k such that A001358(i) + k = 2^j}.
%e A117406 a(0) = 3 because 2^0 + 3 = 4 = A001358(1) and no semiprime is closer 
               to 2^0.
%e A117406 a(1) = 2 because 2^1 + 2 = 4 = A001358(1) and no semiprime is closer 
               to 2^1.
%e A117406 a(2) = 0 because 2^2 + 0 = 4 = A001358(1) and no semiprime is closer 
               to 2^2.
%e A117406 a(3) = 1 because 2^3 + 1 = 9 = 3^2 = A001358(3), no semiprime is closer 
               to 2^3.
%e A117406 a(4) = -2 because 2^4 - 2 = 14 = 2 * 7 = A001358(5), no semiprime is 
               closer.
%e A117406 a(5) = 1 because 2^5 + 1 = 33 = 3 * 11 and no semiprime is closer to 
               2^5.
%e A117406 a(6) = 1 because 2^6 + 1 = 65 = 5 * 13 and no semiprime is closer to 
               2^6.
%e A117406 a(7) = 1 because 2^7 + 1 = 129 = 3 * 43 and no semiprime is closer to 
               2^7.
%e A117406 a(8) = -2 because 2^8 - 2 = 254 = 2 * 127 and no semiprime is closer 
               to 2^8.
%Y A117406 Cf. A000079, A001358, A117387, A117405.
%Y A117406 Sequence in context: A116604 A138741 A079618 this_sequence A151844 A008783 
               A139144
%Y A117406 Adjacent sequences: A117403 A117404 A117405 this_sequence A117407 A117408 
               A117409
%K A117406 easy,sign,less
%O A117406 0,1
%A A117406 Jonathan Vos Post (jvospost3(AT)gmail.com), Mar 13 2006