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 A297121 Self-describing sequence: sequence starts with a(1) = 2 and a(n) is chosen to be the smallest positive number not already in the sequence such that the assertion "sequence gives the positions of the even digits when the sequence is read as a string of digits" is true. 1
 2, 4, 1, 6, 7, 8, 20, 10, 12, 14, 16, 18, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 21, 19, 23, 25, 37, 39, 41, 43, 45, 57, 59, 61, 63, 65, 77, 79, 81, 83, 85, 99, 104, 106, 112 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Inspired by Sloane's sequence A125132. LINKS Jean-Marc Falcoz, Table of n, a(n) for n = 1..2001 EXAMPLE Here are the digits strung together (the even digits occur at positions that are indexed by terms of the sequence): -241678201 0121416182 2242628303 2343638404... Explanation: a(2) must be even, so a(2)=4; a(3)=1; a(4) must be even, so a(4)=6; a(5) cannot be 3 or 5 (contradiction) thus a(5)=7. And so on. CROSSREFS Sequence in context: A019680 A249144 A080032 * A105357 A167546 A011369 Adjacent sequences:  A297118 A297119 A297120 * A297122 A297123 A297124 KEYWORD base,nonn AUTHOR Eric Angelini and Jean-Marc Falcoz, Dec 26 2017 STATUS approved

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Last modified January 17 16:50 EST 2019. Contains 319235 sequences. (Running on oeis4.)