A199986 Numbers with digital product = 2.

2, 12, 21, 112, 121, 211, 1112, 1121, 1211, 2111, 11112, 11121, 11211, 12111, 21111, 111112, 111121, 111211, 112111, 121111, 211111, 1111112, 1111121, 1111211, 1112111, 1121111, 1211111, 2111111, 11111112, 11111121, 11111211, 11112111, 11121111, 11211111

Offset: 1

Author

Jaroslav Krizek, Nov 13 2011

Keywords

• nonn
• easy
• base

Comments

Subsequence of A034049.

Links

• Robert Israel, Table of n, a(n) for n = 1..10000
• S. Giraudo, Combinatorial operads from monoids, arXiv preprint arXiv:1306.6938 [math.CO], 2013-2015. See Sect. 3.2.1.

Programs

Maple

f:= proc(d) local b,i;
  b:= (10^d-1)/9;
  seq(b+10^i,i=0..d-1);
end proc:
seq(f(d),d=1..9); # Robert Israel, Jan 13 2021

PARI

one(n)=if(n,10^n\9,"")
for(n=0,9,for(m=0,n,print1(one(n-m)2one(m)", "))) \\ Charles R Greathouse IV, Nov 13 2011

Python

def athrough(k1s):
  return [int("1"*(i-j)+"2"+"1"*j) for i in range(k1s+1) for j in range(i+1)]
print(athrough(8)) # Michael S. Branicky, Feb 12 2021