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Search: id:A161168
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| 2, 6, 20, 72, 272, 1056, 4160, 16512, 65792, 262656, 1049600, 4196352, 16781312, 67117056, 268451840, 1073774592, 4295032832, 17180000256, 68719738880, 274878431232, 1099512676352, 4398048608256, 17592190238720, 70368752566272
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OFFSET
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0,1
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COMMENT
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Essentially a duplicate of A063376.
a(n) written in base 2: a(0) = 10, a(n) for n >= 1: 110, 10100, 1001000, 100010000, ..., i.e. number 1, (n-1) times 0, number 1, n times 0 (see A163664). a(n) is a bisection of A005418. [From Jaroslav Krizek (jaroslav.krizek(AT)atlas.cz), Aug 14 2009]
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FORMULA
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a(n)=2^n + 4^n.
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PROGRAM
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(Other) 1. sage: [2^n + 4^n for n in xrange(0, 25)] # 2. sage: [sigma(4, n)-1for n in xrange(0, 25)] #
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CROSSREFS
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Sequence in context: A049141 A049129 A063376 this_sequence A049139 A071356 A141200
Adjacent sequences: A161165 A161166 A161167 this_sequence A161169 A161170 A161171
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KEYWORD
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nonn
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AUTHOR
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Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 04 2009
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