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A135576
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Numbers whose binary expansion has only the digit "1" as first, central and final digit.
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6
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1, 7, 21, 73, 273, 1057, 4161, 16513, 65793, 262657, 1049601, 4196353, 16781313, 67117057, 268451841, 1073774593, 4295032833, 17180000257, 68719738881, 274878431233, 1099512676353, 4398048608257, 17592190238721
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| This sequence is essentially identical to A001576.
a(n) is the number whose binary representation is A135577(n), (See example). [From Omar E. Pol (info(AT)polprimos.com), Nov 18 2008]
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FORMULA
| a(1)=1. If n>1 then a(n)=A001576(n-1)
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EXAMPLE
| --------------------------------------
n ........ a(n) ..... a(n) in base 2
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1 .......... 1 ............ 1
2 .......... 7 ........... 111
3 ......... 21 .......... 10101
4 ......... 73 ......... 1001001
5 ........ 273 ........ 100010001
6 ....... 1057 ....... 10000100001
7 ....... 4161 ...... 1000001000001
8 ...... 16513 ..... 100000010000001
9 ...... 65793 .... 10000000100000001
10 .... 262657 ... 1000000001000000001
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MATHEMATICA
| nxt[n_]:=Module[{l=Floor[IntegerLength[n, 2]/2]}, FromDigits[Join[{1}, Table[0, {l}], {1}, Table[0, {l}], {1}], 2]]
NestList[nxt, 1, 25] [From Harvey P. Dale, Dec. 29, 2010]
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CROSSREFS
| Cf. A001576, A135577.
Sequence in context: A152671 A113859 A146533 * A153497 A146247 A147003
Adjacent sequences: A135573 A135574 A135575 * A135577 A135578 A135579
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KEYWORD
| nonn,base
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AUTHOR
| Omar E. Pol (info(AT)polprimos.com), Feb 24 2008, Dec 27 2008
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