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A287515
a(n) = position of n-th 0 when sequence is written in base 2.
1
2, 7, 8, 9, 11, 12, 15, 20, 21, 27, 29, 30, 32, 34, 38, 44, 50, 52, 53, 54, 55, 56, 58, 59, 60, 62, 64, 65, 68, 70, 73, 74, 77, 78, 80, 83, 85, 86, 89, 91, 95, 98, 101, 108, 109, 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
OFFSET
1,1
COMMENTS
A167500 lists the positions of 1's when the sequence is written in binary. This sequence lists the positions of 0's. 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 0's are detected in it.
LINKS
FORMULA
a(n) = zeropos([sequence],n).
EXAMPLE
a(1) = zeropos([10...],1) = 2,
a(2) = zeropos([10,111,1000...],2) = 7,
a(3) = zeropos([10,111,1000...],3) = 8,
a(4) = zeropos([10,111,1000...],4) = 9,
a(5) = zeropos([10,111,1000,1001...],5) = 11.
PROG
(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; ); ); }
CROSSREFS
Sequence in context: A064517 A270804 A167457 * A260581 A179772 A047354
KEYWORD
nonn,base,easy
AUTHOR
Anthony Sand, May 26 2017
STATUS
approved