login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A201015 Composite numbers whose product of digits is 2. 0

%I

%S 12,21,112,121,1112,1121,1211,11112,11121,11211,12111,21111,111112,

%T 121111,211111,1111112,1111121,1112111,1121111,1211111,2111111,

%U 11111112,11111121,11111211,11112111,11121111,11211111,12111111,21111111,111111112,111111121,111111211

%N Composite numbers whose product of digits is 2.

%C Complement of A107612 with respect to A199986. Subsequence of A199981 (composite numbers whose multiplicative digital root is 2).

%e Number 121 is in sequence because 1*2*1=2.

%t Sort[Select[FromDigits/@Flatten[Table[Permutations[Join[{2}, PadRight[ {},n,1]]],{n,10}],1],CompositeQ]] (* _Harvey P. Dale_, Oct 23 2015 *)

%Y Cf. A107612 (primes whose product of digits is 2), A199986 (numbers whose product of digits is 2).

%K nonn,base

%O 1,1

%A _Jaroslav Krizek_, Nov 25 2011

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 5 02:28 EDT 2020. Contains 333238 sequences. (Running on oeis4.)