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A143114
a(n) = the smallest positive integer that is coprime to n and has the same number of (nonleading) 0's in its binary representation as n has in binary.
2
1, 5, 1, 9, 2, 5, 1, 17, 4, 9, 2, 19, 2, 5, 1, 33, 8, 17, 4, 17, 4, 9, 2, 17, 4, 9, 2, 9, 2, 11, 1, 65, 16, 33, 8, 67, 8, 17, 4, 33, 8, 17, 4, 17, 4, 9, 2, 67, 8, 17, 4, 17, 4, 19, 2, 17, 4, 9, 2, 19, 2, 5, 1, 129, 32, 65, 16, 65, 16, 33, 8, 65, 16, 33, 8, 33, 8, 17, 4, 131, 16, 33, 8, 67
OFFSET
1,2
LINKS
EXAMPLE
For n = 20: 20 in binary is 10100, which has three 0's. The positive integers that each have three 0's in their binary representations are 8,17,18,20, etc. The smallest of these that is coprime to 20 is 17. So a(20) = 17.
MATHEMATICA
spi[n_]:=Module[{z=DigitCount[n, 2, 0], k=1}, While[DigitCount[k, 2, 0]!=z || !CoprimeQ[ k, n], k++]; k]; Array[spi, 90] (* Harvey P. Dale, Apr 19 2016 *)
CROSSREFS
Cf. A143113.
Sequence in context: A147319 A147326 A336048 * A103133 A098318 A360750
KEYWORD
base,nonn
AUTHOR
Leroy Quet, Jul 25 2008
EXTENSIONS
a(21) to a(200) from Owen Whitby, Oct 22 20=
STATUS
approved