This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A048991 Write down the numbers 1,2,3,... but omit any number (such as 12 or 23 or 31 ...) which appears in the concatenation of all earlier terms. 18
 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 32, 33, 35, 36, 37, 38, 39, 40, 43, 44, 46, 47, 48, 49, 50, 54, 55, 57, 58, 59, 60, 65, 66, 68, 69, 70, 76, 77, 79, 80, 87, 88, 90, 99, 100, 102, 103, 104, 105, 106, 107, 108, 109, 110, 112 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES Invented by 10-year-old Hannah Rollman. LINKS T. D. Noe, Table of n, a(n) for n=1..10000 Nick Hobson, Python program for this sequence EXAMPLE 12 is omitted since we see "1,2" at the beginning of the sequence; 101 is omitted because we can see "10,1[1]"; etc. MATHEMATICA Clear[a]; a[1] = 1; s = "1"; a[n_] := a[n] = Catch[ For[k = a[n-1] + 1, True, k++, If[ StringFreeQ[s, t = ToString[k]], s = s <> t; Throw[k] ] ] ]; Table[a[n], {n, 1, 75}] (* Jean-François Alcover, Jan 09 2013 *) PROG (Python) see Hobson link (Haskell) import Data.List (isInfixOf) a048991 n = a048991_list !! (n-1) a048991_list = f [1..] [] where    f (x:xs) ys | xs' `isInfixOf` ys = f xs ys                | otherwise          = x : f xs (xs' ++ ys)                where xs' = reverse \$ show x -- Reinhard Zumkeller, Dec 05 2011 CROSSREFS See A048992 for the omitted numbers. Cf. A105390. Sequence in context: A023753 A035332 A318536 * A321292 A131881 A053460 Adjacent sequences:  A048988 A048989 A048990 * A048992 A048993 A048994 KEYWORD nonn,nice,base,easy AUTHOR Bernardo Recamán (ignotus(AT)hotmail.com) EXTENSIONS Edited by Patrick De Geest, Jun 02 2003 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 17 22:31 EDT 2019. Contains 328134 sequences. (Running on oeis4.)