OFFSET
1,2
COMMENTS
The sequence is infinite because if k is a term, then 10*k is also a term.
Every number k of the form 44...45 (one of more 4's followed by 5, cf. A093140) is a term because 3*k = 133...35 and 7*k = 311...15.
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..10000
EXAMPLE
k = 75 is a term because 3*k = 225 and 7*k = 525 share the same set of digits, namely {2,5}.
k = 423 is a term because 3*k = 1269 and 7*k = 2961 share the same set of digits, namely {1,2,6,9}.
MATHEMATICA
Select[Range[0, 11000], Union[IntegerDigits[3*#]] == Union[IntegerDigits[7*#]] &] (* Amiram Eldar, May 18 2023 *)
PROG
(PARI) isok(k) = Set(digits(3*k)) == Set(digits(7*k));
(Python)
def ok(n): return set(str(3*n)) == set(str(7*n))
print([k for k in range(11000) if ok(k)]) # Michael S. Branicky, May 04 2023
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Alexandru Petrescu, May 04 2023
STATUS
approved