OFFSET
1,2
COMMENTS
LINKS
Stephanus Gibbs, Roman Numeral and Date Conversion
Gerard Schildberger, The first 3999 numbers in Roman numerals
Eric Weisstein's World of Mathematics, Roman Numerals
Wikipedia, Roman numerals
EXAMPLE
a(1) = 1 because Roman(1) = I and Reversal(I) = I, which is Roman.
a(4) = 4 because Roman(4) = IV and Reversal(IV) = VI, which is Roman.
a(10) = 19 because Roman(19) = XIX which is a palindromic Roman numeral.
a(27) = 900 because Roman(900) = CM and Reversal(CM) = MC, which is Roman.
40 == XL -> LX == 60, therefore 40 and 60 are terms.
1999 is not in the sequence because "MIM" is not a well-formed Roman numeral for 1999, although it looks like one; see Schildberger.
MATHEMATICA
Select[Range[3000], RomanNumeral[FromRomanNumeral[#]] == # & [StringReverse[RomanNumeral[#]]] &] (* Paolo Xausa, Mar 03 2024 *)
PROG
(Haskell)
a093703 n = a093703_list !! (n-1)
a093703_list = filter
((`elem` map a061493 [1..3999]) . a004086 . a061493) [1..]
-- Reinhard Zumkeller, Apr 14 2013
CROSSREFS
KEYWORD
nonn,base,fini,full
AUTHOR
Reinhard Zumkeller, May 17 2004
EXTENSIONS
Added sections of text from the erroneous A123054. - N. J. A. Sloane, Apr 15 2013
STATUS
approved