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 A213006 Positive numbers that, spelled in English, are as long as the spelling of their digits. 2
 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 15, 18, 1001, 1002, 1003, 1004, 1005, 1006, 1007, 1008, 1009, 1010, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 3001, 3002, 3003, 3004, 3005, 3006, 3007, 3008, 3009, 3010, 4001, 4002, 4003, 4004, 4005, 4006, 4007, 4008, 4009, 4010, 5001, 5002, 5003, 5004, 5005, 5006, 5007, 5008, 5009, 5010, 6001, 6002, 6003 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Dan Hoey came up with an inequality Spell_Length(n)<=A*n+B (I've forgotten A and B, which are fairly small rationals: equality at two points), that was used to limit the maximum length of a self-enumerating sentence, and thus make an exhaustive search possible. - R. H. Hardin, Feb 22 2012 REFERENCES Eric Angelini, Posting to Sequence Fans Mailing List, Feb 12 2012 Hans Havermann, Posting to Sequence Fans Mailing List, Feb 23 2012 LINKS Hans Havermann, Table of n, a(n) for n = 1..10000 EXAMPLE 11 = eleven (6 letters) = one one (6 letters) 1002 = one thousand two (14 letters) = one zero zero two (14 letters). PROG (Python) from num2words import num2words as n2w m = {"0":4, "1":3, "2":3, "3":5, "4":4, "5":4, "6":3, "7":5, "8":5, "9":4} def dl(n): return sum(m[d] for d in str(n)) def wl(n): return sum(1 for c in n2w(n).replace(" and", "") if c.isalpha()) def ok(n): return dl(n) == wl(n) print([k for k in range(1, 7000) if ok(k)]) # Michael S. Branicky, Apr 03 2023 CROSSREFS Sequence in context: A037173 A091897 A055201 * A068998 A072303 A242413 Adjacent sequences: A213003 A213004 A213005 * A213007 A213008 A213009 KEYWORD nonn,base,word AUTHOR N. J. A. Sloane, Jun 01 2012 STATUS approved

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Last modified April 23 23:26 EDT 2024. Contains 371917 sequences. (Running on oeis4.)