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Composite numbers whose multiplicative digital root is 4.
1

%I #12 Apr 28 2018 16:20:10

%S 4,14,22,27,39,72,93,98,114,122,141,172,189,198,212,217,221,249,266,

%T 294,319,333,338,346,364,391,411,429,436,492,626,634,662,712,721,767,

%U 772,776,793,819,833,891,913,918,924,931,942,973,981,1114,1122,1127,1139

%N Composite numbers whose multiplicative digital root is 4.

%C Complement of A199983 with respect to A034051.

%e Number 172 is in sequence because 1*7*2=14, 1*4=4.

%t cn4Q[n_]:=NestWhile[Times@@IntegerDigits[#]&,n,#>9&]==4; Select[Select[ Range[ 1200],CompositeQ],cn4Q] (* _Harvey P. Dale_, Apr 28 2018 *)

%Y Cf. A199983 (primes whose multiplicative digital root is 4).

%Y Cf. A034051 (numbers whose multiplicative digital root is 4).

%K nonn,base

%O 1,1

%A _Jaroslav Krizek_, Nov 13 2011