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A055247 Related to A055246 and A005836. Used for boundaries of open intervals which have to be erased in the Cantor middle third set construction. 3
1, 2, 7, 8, 19, 20, 25, 26, 55, 56, 61, 62, 73, 74, 79, 80, 163, 164, 169, 170, 181, 182, 187, 188, 217, 218, 223, 224, 235, 236, 241, 242, 487, 488, 493, 494, 505, 506, 511, 512, 541, 542, 547, 548, 559, 560, 565, 566, 649, 650, 655, 656 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

At step number k >= 1 the 2^(k-1) open intervals which are erased from [0,1] in the Cantor middle third set construction are: I(k,n)=(a(2*n-1)/3^k,a(2*n)/3^k), n=1,.,2^(k-1).

LINKS

Table of n, a(n) for n=1..52.

FORMULA

a(n)= A055246((n+1)/2) if n odd, a(n)= A055246(n/2)+1 if n even. A055246(n)= 1+6*A005836(n-1), n >= 1.

a(1) = 1, a(n) = 3^ceiling( log_2( n ) ) - a( 2^ceiling( log_2( n ) ) + 1 - n ). - Juan Jose Alba Gonzalez (jjalba(AT)gmail.com), May 16 2006

EXAMPLE

k=1: (1/3, 2/3); k=2: (1/9, 2/9), (7/9, 8/9); k=3: (1/27, 2/27), (7/27, 8/27), (19/27, 20/27), (25/27, 26/27); ...

CROSSREFS

Cf. A005836, A055246.

Sequence in context: A213037 A287343 A101518 * A015617 A306903 A026579

Adjacent sequences:  A055244 A055245 A055246 * A055248 A055249 A055250

KEYWORD

nonn,easy

AUTHOR

Wolfdieter Lang, May 23 2000

STATUS

approved

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Last modified February 27 11:38 EST 2021. Contains 341656 sequences. (Running on oeis4.)