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 A084383 a(0)=0; for n>0, a(n) = smallest number that is not a concatenation of any number of distinct earlier terms in increasing order. 4
 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 20, 21, 22, 30, 31, 32, 33, 40, 41, 42, 43, 44, 50, 51, 52, 53, 54, 55, 60, 61, 62, 63, 64, 65, 66, 70, 71, 72, 73, 74, 75, 76, 77, 80, 81, 82, 83, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS After 11 we can see 1,2 -> 12, 1,3 -> 13, etc., but not 20. LINKS Michael S. Branicky, Table of n, a(n) for n = 0..10000 PROG (Python) from itertools import islice def incats(s, L): if s == "": return True return any(s.startswith(w) and incats(s[len(w):], L[i+1:]) for i, w in enumerate(L)) def agen(): # generator of terms L, an, s = ["0"], 1, "1" yield from [0] while True: yield an L.append(s) while incats((s:=str(an)), L): an += 1 print(list(islice(agen(), 70))) # Michael S. Branicky, Feb 01 2024 CROSSREFS Hannah Rollman's numbers: A048991, A048992. Sequence in context: A247758 A247757 A247754 * A032873 A072543 A009996 Adjacent sequences: A084380 A084381 A084382 * A084384 A084385 A084386 KEYWORD nonn,base AUTHOR Amarnath Murthy, May 29 2003 EXTENSIONS More terms from Patrick De Geest, Jun 03 2003 STATUS approved

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Last modified April 23 10:29 EDT 2024. Contains 371905 sequences. (Running on oeis4.)