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A032917 Numbers having only digits 1 and 3 in their decimal representation. 14
1, 3, 11, 13, 31, 33, 111, 113, 131, 133, 311, 313, 331, 333, 1111, 1113, 1131, 1133, 1311, 1313, 1331, 1333, 3111, 3113, 3131, 3133, 3311, 3313, 3331, 3333, 11111, 11113, 11131, 11133, 11311, 11313, 11331, 11333, 13111, 13113 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Numbers n such that product of digits of n is a power of 3. - Vincenzo Librandi Aug 19 2016
LINKS
MATHEMATICA
Flatten[Table[FromDigits[#, 10]&/@Tuples[{1, 3}, n], {n, 5}]] (* Vincenzo Librandi, Jun 02 2012 *)
PROG
(Magma) [n: n in [1..14000] | Set(IntegerToSequence(n, 10)) subset {1, 3}]; // Vincenzo Librandi, Jun 02 2012
(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
(Python)
def a(n): return int(bin(n+1)[3:].replace('1', '3').replace('0', '1'))
print([a(n) for n in range(1, 45)]) # Michael S. Branicky, May 13 2021
(Python)
def A032917(n): return (int(bin(m:=n+1)[3:])<<1) + (10**(m.bit_length()-1)-1)//9 # Chai Wah Wu, Oct 13 2023
CROSSREFS
CF. A020451 (primes).
Sequence in context: A287348 A019374 A033680 * A006559 A023248 A199341
KEYWORD
nonn,base
AUTHOR
EXTENSIONS
Definition reworded by M. F. Hasler, Mar 10 2014
STATUS
approved

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Last modified July 25 11:18 EDT 2024. Contains 374588 sequences. (Running on oeis4.)