

A121305


Value of Roman numeral embedded in English name of n, or 0 if no such value exists.


2



0, 0, 0, 0, 0, 4, 9, 5, 1, 1, 0, 55, 55, 1, 0, 1, 9, 5, 1, 1, 0, 0, 0, 0, 0, 4, 9, 5, 1, 1, 1, 1, 1, 1, 1, 0, 0, 4, 2, 2, 0, 0, 0, 0, 0, 4, 9, 5, 1, 1, 1, 1, 1, 1, 1, 0, 0, 4, 2, 2, 9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 5, 5, 5, 5, 0, 0, 0, 6, 6, 1, 1, 1, 1, 1, 0, 0, 4, 2, 2, 1, 1, 1, 1, 1, 0, 0, 4, 2, 2, 0
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

0,6


COMMENTS

Not welldefined! A002904 is the main entry for this sequence.  N. J. A. Sloane, Sep 28 2011.
There are a finite number of nonzero values because "hunDreD" and "mILLIon" and "bILLIon" and "trILLIon" and so forth yield nonwellformed Roman numerals. The largest n such that a(n) is nonzero is 94044 maps to "nInetyfour thousanD fortyfour" maps to "ID" maps to 499.
Allowing a(94044) = 499 because of "ID" speaks to the nonstandard usage (499 = "CDXCIX") that makes this sequence, as mentioned above, not necessarily welldefined. If "ID" is ok, why not "IIV" for a(35)? If we take Mathematica's RomanNumeral conversion as standard (for integers 14999; starting with 5000 we generate overbars), then there are 1411 nonzero entries up to and including a(44099) = 502. Specifically, I (30 solutions), II (8), IV (7), V (9), VI (2), IX (9), LV (2), D (272), DI (480), DII (128), DIV (112), DV (144), DVI (32), DIX (144), and DLV (32).  Hans Havermann, May 06 2019


LINKS

Table of n, a(n) for n=0..100.
Brady Haran and N. J. A. Sloane, What Number Comes Next? (2018), Numberphile video


FORMULA

Take English name of n as string of characters, eliminate all spaces, hyphens and letters other than I, V, X, L, C, D, M. Interpret remaining string as a Roman numeral, assigning 0 if the string is not wellformed and a(n) is wellformed.


EXAMPLE

a(5) = 4 because 5 maps to "five" maps to "fIVe" maps to "IV" maps to 4.
a(6) = 9 because 6 maps to "six" maps to "sIX" maps to "IX" maps to 9.
a(7) = 5 because 7 maps to "seven" maps to "seVen" maps to "V" maps to 5.
a(8) = 1 because 8 maps to "eight" maps to "eIght" maps to "I" maps to 1.
a(9) = 1 because 9 maps to "nine" maps to "nIne" maps to "I" maps to 1.
a(35) = 0 because 35 maps to "thirtyfive" maps to "thIrtyfIVe" maps to "IIV" which is not a wellformed Roman nhumeral, hence maps to 0.
a(1000) = 500 because 1000 maps to "one thousand" maps to "one thousanD" maps to "D" maps to 500.


CROSSREFS

Cf. A002904, A005589.
Sequence in context: A200629 A021206 A002904 * A200396 A011513 A164818
Adjacent sequences: A121302 A121303 A121304 * A121306 A121307 A121308


KEYWORD

base,easy,nonn,word


AUTHOR

Jonathan Vos Post, Sep 05 2006


STATUS

approved



