A032917 - OEIS

%I #30 Oct 13 2023 12:23:08

%S 1,3,11,13,31,33,111,113,131,133,311,313,331,333,1111,1113,1131,1133,

%T 1311,1313,1331,1333,3111,3113,3131,3133,3311,3313,3331,3333,11111,

%U 11113,11131,11133,11311,11313,11331,11333,13111,13113

%N Numbers having only digits 1 and 3 in their decimal representation.

%C Numbers n such that product of digits of n is a power of 3. - _Vincenzo Librandi_ Aug 19 2016

%H Vincenzo Librandi, <a href="/A032917/b032917.txt">Table of n, a(n) for n = 1..1000</a>

%t Flatten[Table[FromDigits[#,10]&/@Tuples[{1,3},n],{n,5}]] (* _Vincenzo Librandi_, Jun 02 2012 *)

%o (Magma) [n: n in [1..14000] | Set(IntegerToSequence(n, 10)) subset {1, 3}]; // _Vincenzo Librandi_, Jun 02 2012

%o (PARI) for(n=1, 5, p=2*vector(n, i, 10^(n-i))~; forvec(d=vector(n, i, [1, 3]/2), print1(d*p,","))) \\ _M. F. Hasler_, Mar 10 2014

%o (Python)

%o def a(n): return int(bin(n+1)[3:].replace('1', '3').replace('0', '1'))

%o print([a(n) for n in range(1, 45)]) # _Michael S. Branicky_, May 13 2021

%o (Python)

%o def A032917(n): return (int(bin(m:=n+1)[3:])<<1) + (10**(m.bit_length()-1)-1)//9 # _Chai Wah Wu_, Oct 13 2023

%Y CF. A020451 (primes).

%K nonn,base

%O 1,2

%A _Clark Kimberling_

%E Definition reworded by _M. F. Hasler_, Mar 10 2014