OFFSET
1,1
MATHEMATICA
Select[Range[300], DigitCount[#, 4, 0]==DigitCount[#, 4, 3]>0&] (* Harvey P. Dale, Oct 30 2021 *)
PROG
(Python)
from sympy.ntheory import count_digits
def ok(n): c = count_digits(n, 4); return c[0] == c[3] > 0
print([k for k in range(300) if ok(k)]) # Michael S. Branicky, Dec 19 2021
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
STATUS
approved