OFFSET
1,1
LINKS
Wikipedia, Roman numerals
EXAMPLE
4, written IV, and 8, written VIII, are terms.
14, written XIV, is not a term.
MATHEMATICA
kmax=502; a={}; For[k=1, k<=kmax, k++, If[Length[DeleteDuplicates[Characters[RomanNumeral[k]]]] == 2, AppendTo[a, k]]]; a (* Stefano Spezia, Aug 26 2022 *)
PROG
(Python)
def f(s, k):
return s[:2] if k==4 else (s[1]*(k>=5)+s[0]*(k%5) if k<9 else s[0]+s[2])
def roman(n):
m, c, x, i = n//1000, (n%1000)//100, (n%100)//10, n%10
return "M"*m + f("CDM", c) + f("XLC", x) + f("IVX", i)
def ok(n): return len(set(roman(n))) == 2
print([k for k in range(503) if ok(k)]) # Michael S. Branicky, Aug 24 2022
CROSSREFS
KEYWORD
nonn,base,fini,easy
AUTHOR
Alain Cousquer and Pierre-Hugues Villaume, Aug 24 2022
STATUS
approved