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A287515 a(n) = position of n-th 0 when sequence is written in base 2. 1

%I

%S 2,7,8,9,11,12,15,20,21,27,29,30,32,34,38,44,50,52,53,54,55,56,58,59,

%T 60,62,64,65,68,70,73,74,77,78,80,83,85,86,89,91,95,98,101,108,109,

%U 110,114,116,120,127,128,134,136,137,138,139,140,141,143,144,145,146,147,150,151,152,154,155,157,158,159,162

%N a(n) = position of n-th 0 when sequence is written in base 2.

%C A167500 lists the positions of 1s when the sequence is written in binary. This sequence lists the positions of 0s. When written in binary, it begins 10, 111, 1000, 1001, 1011... The first 0 appears at position 2, so a(1) = 2 = 10. The second 0 appears at position 7, so a(2) = 7 = 111. The third 0 appears at position 8, so a(3) = 8 = 1000. The sequence then becomes self-generating, because entries are added to it faster than 0s are detected in it.

%H Anthony Sand, <a href="/A287515/b287515.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = zeropos([sequence],n)

%e a(1) = zeropos([10...],1) = 2

%e a(2) = zeropos([10,111,1000...],2) = 7

%e a(3) = zeropos([10,111,1000...],3) = 8

%e a(4) = zeropos([10,111,1000...],4) = 9

%e a(5) = zeropos([10,111,1000,1001...],5) = 11

%o (PARI) { zeroposseq()= smx=100; s=vector(smx); s[1]=2; s[2]=7; s[3]=8; si=0; dig=digits(s[1],2); di=1; i=1; dl=0; while(si<smx, d=dig[i]; dl++; if(d==0, si++; s[si]=dl; print1(dl,", "); ); i++; if(i>#dig, di++; dig=digits(s[di],2); i=1; ); ); }

%Y Cf. A167500, A167502.

%K nonn,base,easy

%O 1,1

%A _Anthony Sand_, May 26 2017

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Last modified November 19 18:39 EST 2019. Contains 329323 sequences. (Running on oeis4.)