A199986 - OEIS

%I #27 Feb 12 2021 14:52:16

%S 2,12,21,112,121,211,1112,1121,1211,2111,11112,11121,11211,12111,

%T 21111,111112,111121,111211,112111,121111,211111,1111112,1111121,

%U 1111211,1112111,1121111,1211111,2111111,11111112,11111121,11111211,11112111,11121111,11211111

%N Numbers with digital product = 2.

%C Subsequence of A034049.

%H Robert Israel, <a href="/A199986/b199986.txt">Table of n, a(n) for n = 1..10000</a>

%H S. Giraudo, <a href="http://arxiv.org/abs/1306.6938">Combinatorial operads from monoids</a>, arXiv preprint arXiv:1306.6938 [math.CO], 2013-2015. See Sect. 3.2.1.

%p f:= proc(d) local b,i;

%p   b:= (10^d-1)/9;

%p   seq(b+10^i,i=0..d-1);

%p end proc:

%p seq(f(d),d=1..9); # _Robert Israel_, Jan 13 2021

%o (PARI) one(n)=if(n,10^n\9,"")

%o for(n=0,9,for(m=0,n,print1(one(n-m)2one(m)", "))) \\ _Charles R Greathouse IV_, Nov 13 2011

%o (Python)

%o def athrough(k1s):

%o   return [int("1"*(i-j)+"2"+"1"*j) for i in range(k1s+1) for j in range(i+1)]

%o print(athrough(8)) # _Michael S. Branicky_, Feb 12 2021

%K nonn,easy,base

%O 1,1

%A _Jaroslav Krizek_, Nov 13 2011