|
%I #7 Dec 26 2017 17:32:39
%S 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,
%T 48,50,52,54,56,58,60,62,64,66,68,70,72,74,76,78,80,82,84,86,88,90,92,
%U 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
%N 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.
%C Inspired by Sloane's sequence A125132.
%H Jean-Marc Falcoz, <a href="/A297121/b297121.txt">Table of n, a(n) for n = 1..2001</a>
%e Here are the digits strung together (the even digits occur at positions that are indexed by terms of the sequence):
%e -241678201
%e 0121416182
%e 2242628303
%e 2343638404...
%e 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.
%K base,nonn
%O 1,1
%A _Eric Angelini_ and _Jean-Marc Falcoz_, Dec 26 2017
|
