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A199921
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Number of Roman numerals < 4000 with n letters.
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4
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7, 31, 93, 215, 389, 573, 691, 691, 573, 389, 215, 93, 31, 7, 1
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graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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Note that the sequence is completely symmetrical with the addition of the single (notional) Roman string of length zero. - Ian Duff, Jun 27 2017
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LINKS
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EXAMPLE
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a(1) = 7, since there are the seven one-letter roman numerals I, V, X, L, C, D, M.
a(15) = 1, since there is one fifteen-letter roman numeral MMMDCCCLXXXVIII.
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MAPLE
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for i from 1 to 15 do L[i]:={}: od: for n from 1 to 3999 do L[length(convert(n, roman))]:={op(L[length(convert(n, roman))]), n}; od:
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MATHEMATICA
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romanLetterCount = Table[0, {15}]; j = 1; While[j < 4000, romanLetterCount[[StringLength[IntegerString[j, "Roman"]]]]++; j++]; romanLetterCount (* Alonso del Arte, Nov 12 2011 *)
Rest[BinCounts[StringLength[RomanNumeral[Range[3999]]]]] (* Paolo Xausa, Mar 19 2024 *)
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PROG
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(Haskell)
import Data.List (group, sort)
a199921 n = a199921_list !! (n-1)
a199921_list = map length $ group $ sort $ map (a055642 . a061493) [1..3999]
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CROSSREFS
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KEYWORD
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nonn,fini,full
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AUTHOR
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STATUS
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approved
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