%I #10 Aug 03 2014 14:01:36

%S 12,21,26,34,62,112,121,126,134,143,162,216,232,261,278,279,287,297,

%T 299,314,322,341,369,371,376,396,398,413,447,469,474,496,612,621,637,

%U 639,649,666,693,694,713,728,729,731,736,744,763,782,792,872,893,927,936

%N Composite numbers whose multiplicative digital root is 2.

%C Complement of A199980 with respect to A034049.

%e Number 278 is in sequence because 2*7*8=112, 1*1*2 =2.

%t t = {}; n = 0; While[Length[t] < 100, n = n + 1; If[! PrimeQ[n], s = n; While[s >= 10, s = Times @@ IntegerDigits[s]]; If[s == 2, AppendTo[t, n]]]]; t (* _T. D. Noe_, Nov 16 2011 *)

%Y Cf. A199980 (primes whose multiplicative digital root is 2).

%Y Cf. A034049 (numbers whose multiplicative digital root is 2).

%K nonn,base

%O 1,1

%A _Jaroslav Krizek_, Nov 13 2011