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A066532
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If n is odd a(n) = 1, if n is even a(n) = 2^(n-1).
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1
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1, 2, 1, 8, 1, 32, 1, 128, 1, 512, 1, 2048, 1, 8192, 1, 32768, 1, 131072, 1, 524288, 1, 2097152, 1, 8388608, 1, 33554432, 1, 134217728, 1, 536870912, 1, 2147483648, 1, 8589934592, 1, 34359738368, 1, 137438953472, 1, 549755813888, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Size of Frattini subgroup of the group of n X n signed permutations matrices (described in sequence A066051).
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,350
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FORMULA
| G.f.: G.f.: 1/(1-x^2)+2x(1+2x^2)/(1-2x^2); a(n)=2^n*(1-(-1)^n)/2+(1+(-1)^n)/2. - Paul Barry (pbarry(AT)wit.ie), Jun 17 2006
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MATHEMATICA
| Table[ If[ OddQ[n], 1, 2^(n - 1)], {n, 1, 42} ]
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PROG
| (PARI) { for (n=1, 350, if (n%2, a=1, a=2^(n-1)); write("b066532.txt", n, " ", a) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Feb 22 2010]
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CROSSREFS
| Cf. A066051.
Sequence in context: A101280 A008309 A131175 * A205397 A020778 A118961
Adjacent sequences: A066529 A066530 A066531 * A066533 A066534 A066535
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KEYWORD
| nonn,easy
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AUTHOR
| Sharon Sela (sharonsela(AT)hotmail.com), Jan 06 2002
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 07 2002
More terms from Ralf Stephan (ralf(AT)ark.in-berlin.de), Jul 25 2003
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