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Search: id:A129771
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| 3, 5, 9, 15, 17, 23, 27, 29, 33, 39, 43, 45, 51, 53, 57, 63, 65, 71, 75, 77, 83, 85, 89, 95, 99, 101, 105, 111, 113, 119, 123, 125, 129, 135, 139, 141, 147, 149, 153, 159, 163, 165, 169, 175, 177, 183, 187, 189, 195, 197, 201, 207, 209, 215, 219, 221, 225, 231, 235
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A heuristic argument suggests that, as n tends to infinity, a(n)/n converges to 4. - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), May 17 2007
These numbers may be called primitive evil numbers because every evil number is a power of twice one of these numbers. Note that the difference between consecutive terms is either 2, 4, or 6. - T. D. Noe, Jun 06 2007
A132680(a(n)) = A132680((a(n)-1)/2) + 2. - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 26 2007
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..1000
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FORMULA
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a(n) = 2*A000069(n) + 1. a(n) is 1 plus twice odious numbers. a(n) = A128309(n) + 1. a(n) is 1 plus odious even numbers.
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MATHEMATICA
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Select[Range[300], OddQ[ # ] && EvenQ[DigitCount[ #, 2, 1]] &] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), May 17 2007
Select[Range[300], EvenQ[Plus @@ IntegerDigits[ #, 2]] && OddQ[ # ] &]
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CROSSREFS
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This sequence is the intersection of A001969 (Evil numbers: even number of 1's in binary expansion.) and A005408 (The odd numbers: a(n) = 2n+1.) A093688 (Numbers n such that all divisors of n, excluding the divisor 1, have an even number of 1's in their binary expansions) is a subsequence.
Cf. A092246 (odd odious numbers)
Sequence in context: A120695 A103578 A116649 this_sequence A093688 A143512 A111249
Adjacent sequences: A129768 A129769 A129770 this_sequence A129772 A129773 A129774
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KEYWORD
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nonn
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AUTHOR
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Tanya Khovanova (tanyakh(AT)yahoo.com), May 16 2007
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EXTENSIONS
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More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), May 17 2007
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