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 A303701 Number of distinct letters in the (American) English name of n, excluding spaces and hyphens. 0
 4, 3, 3, 4, 4, 4, 3, 4, 5, 3, 3, 4, 5, 6, 7, 5, 6, 5, 6, 4, 5, 6, 6, 7, 9, 8, 8, 7, 8, 6, 5, 8, 7, 6, 8, 8, 7, 9, 7, 7, 5, 7, 6, 7, 6, 8, 8, 9, 9, 8, 4, 7, 6, 7, 7, 6, 6, 8, 7, 6, 5, 8, 7, 8, 9, 8, 5, 8, 8, 7, 6, 7, 8, 8, 10, 8, 8, 6, 9, 7, 6, 8, 8, 7, 10, 8, 8, 9, 6, 7, 5, 6, 7, 7, 9, 7, 7, 7 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS First occurrence of k=3..23: 1, 0, 8, 13, 14, 25, 24, 74, 112, 127, 125, 165, 265, 1265, 2568, 12468, 1002568, 1001002568, 1000001001002568, 1000000001000001001002568, 1001000000001000001001002568. Since there are no number words consisting of just one or two letters, nor any number words which contain the letters "j", "k" or "z"; the above list is complete. LINKS FORMULA a(n) <= A005589(n). EXAMPLE a(7) = 4 since "seven" has 4 distinct letters. (Cf. A005589(7) = 5.) MATHEMATICA f[n_] := Length@ Union@ StringPartition[ StringReplace[ IntegerName[n, "Words"], ", " | " " | "\[Hyphen]" -> ""], 1]; Array[f, 98, 0] CROSSREFS Cf. A005589. Sequence in context: A188885 A129344 A048853 * A179845 A180217 A270651 Adjacent sequences:  A303698 A303699 A303700 * A303702 A303703 A303704 KEYWORD nonn,word AUTHOR Robert G. Wilson v, Apr 29 2018 STATUS approved

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Last modified March 20 21:49 EDT 2019. Contains 321352 sequences. (Running on oeis4.)