A240135 - OEIS

%I #14 Oct 08 2018 20:24:37

%S 1,3,8,18,40,96,224,480,1024,2304,5120,10752,22528,49152,102400,

%T 212992,442368,917504,1966080,4194304,8650752,17825792,36700160,

%U 75497472,159383552,327155712,671088640,1409286144,2952790016,6039797760,12348030976,25769803776

%N a(n) = composite(n)*2^(n - 3).

%e a(1)=1 because composite(1) * 2^(1-3) = 4 * 2^(-2) = 1;

%e a(2)=3 because composite(2) * 2^(2-3) = 6 * 2^(-1) = 3;

%e a(3)=8 because composite(3) * 2^(3-3) = 8 * 2^0 = 8.

%t #[[1]]*2^(#[[2]]-3)&/@Module[{cs=Select[Range[50],CompositeQ]},Thread[ {cs,Range[Length[cs]]}]] (* _Harvey P. Dale_, Oct 08 2018 *)

%Y Cf. A002808.

%K nonn,less

%O 1,2

%A _Gerasimov Sergey_, Apr 02 2014