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Search: id:A018900
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| A018900 |
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Sum of two distinct powers of 2. |
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+0
22
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| 3, 5, 6, 9, 10, 12, 17, 18, 20, 24, 33, 34, 36, 40, 48, 65, 66, 68, 72, 80, 96, 129, 130, 132, 136, 144, 160, 192, 257, 258, 260, 264, 272, 288, 320, 384, 513, 514, 516, 520, 528, 544, 576, 640, 768, 1025, 1026, 1028, 1032, 1040, 1056
(list; table; graph; listen)
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OFFSET
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1,1
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COMMENT
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Appears to give all n such that 8 is the highest power of 2 dividing A005148 (n). General conjecture: numbers k such that 8^a is the highest power of 2 dividing A005148 (k) is the same sequence as numbers k such that k has exactly (a+1) 1's in his binary representation. - Benoit Cloitre (benoit7848c(AT)orange.fr), Jun 22 2002
Contribution from Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 24 2009: (Start)
A000120(a(n)) = 2;
complement of A161989; A151774(a(n)) = 1;
seen as a triangle read by rows:
T(n,k) = 2^(k-1) + 2^n, 1<=k<=n;
sum of n-th row = A087323(n). (End)
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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^trinv(n-1) + 2^((n-1)-((trinv(n-1)*(trinv(n-1)-1))/2)) i.e. 2^A002024[ n ]+2^A002262[ n-1 ] (the latter sequence contains the definition of trinv) - Antti Karttunen.
a(n) = A059268(n-1) + A140513(n-1). [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 24 2009]
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MATHEMATICA
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Select[ Range[ 1056 ], (Count[ IntegerDigits[ #, 2 ], 1 ]==2)& ]
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CROSSREFS
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Cf. A001969, A048639, A048645.
Sequence in context: A075311 A032786 A080309 this_sequence A126590 A140584 A085705
Adjacent sequences: A018897 A018898 A018899 this_sequence A018901 A018902 A018903
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KEYWORD
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nonn,easy,nice,tabl
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AUTHOR
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Jonn Dalton (jdalton(AT)vnet.ibm.com)
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