

A078715


Palindromic Roman numerals.


7



1, 2, 3, 5, 10, 19, 20, 30, 50, 100, 190, 200, 300, 500, 1000, 1900, 2000, 3000
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graph;
refs;
listen;
history;
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internal format)



OFFSET

1,2


COMMENTS

This sequence is consistent with the Roman numerals as expressed in the Schildberger link. 4 (usually IV now) could be included in a variant of this sequence as IIII is sometimes used (especially on clock faces). To make this or similar sequences welldefined for numbers larger than 3999, it must be decided whether and how to handle the apostrophus (backwardC), the vinculum (bar), the frame, or even other multiplier notations used at various times in representations of larger Roman numerals. Recalling the "Y2K crisis", will there be a(n even milder) "Y4M crisis"? In particular, is 4000 to be represented as MMMM, (I)(I)(I)(I) (where parentheses are used to represent C and the apostrophus), MV (with vinculum over the V), IV (with vinculum over both I and V) or IIII with vinculum over all four I's? If there is no general agreement, could Roman civilization be at risk (once again)?


REFERENCES

Encyclopaedia Britannica, 1981 ed., Vol. 11, "Mathematics, History of", p. 647.
Webster's Third New International Dictionary (Unabridged), 1976 ed., "Cardinal Numbers Table" and footnotes, p. 1549.


LINKS



FORMULA



EXAMPLE

I, II, III, V, X, XIX, XX, XXX, L, C, CXC, CC, CCC, D, M, MCM, MM, MMM


MATHEMATICA

Select[Range[3000], PalindromeQ[RomanNumeral[#]] &] (* Paolo Xausa, Mar 03 2024 *)


PROG

(Haskell)
a078715 n = a078715_list !! (n1)
a078715_list = filter ((== 1) . a136522 . a061493) [1..3999]


CROSSREFS



KEYWORD

base,easy,nonn,fini,full


AUTHOR



STATUS

approved



