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Search: id:A162751
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| A162751 |
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Write down in binary the nth positive (odd) integer that is a palindrome in base 2. Take only the leftmost half of the digits (including the middle digit if there are an odd number of digits). a(n) is the decimal equivalent of the result. |
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+0
1
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| 1, 1, 2, 3, 2, 3, 4, 5, 6, 7, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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Every positive integer occurs exactly twice in this sequence.
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EXAMPLE
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27 is the 9th (odd) palindrome when written in binary. 27 in binary is 11011. Take the leftmost half of the digits (including the middle digit), and we have 110. a(9) is decimal equivalent of this, which is 6.
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MAPLE
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read("transforms3") ; a006995 := BFILETOLIST("b006995.txt") ; chop := proc(L) [op(1.. floor((nops(L)+1)/2), L)] ; end: for n from 2 to 100 do p := op(n, a006995) ; bdgs := chop(convert(p, base, 2)) ; add(op(-i, bdgs)*2^(i-1), i=1..nops(bdgs)) ; printf("%d, ", %) ; end do: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 01 2009]
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CROSSREFS
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A006995
Sequence in context: A106249 A110516 A134986 this_sequence A026342 A078198 A098235
Adjacent sequences: A162748 A162749 A162750 this_sequence A162752 A162753 A162754
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KEYWORD
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base,nonn
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AUTHOR
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Leroy Quet (q1qq2qqq3qqqq(AT)yahoo.com), Jul 12 2009
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 01 2009
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