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A011765
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Period 4: repeat 0,0,0,1.
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7
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0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Arises in connection with leap years, years of U.S. Presidential elections, Olympic Games, etc.
Note that leap years define a sequence with period length 400, unlike A121262 which has period length 4. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Dec 19 2008]
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FORMULA
| G.f.: x^4/(1-x^4). [From Mohammad K. Azarian (azarian(AT)evansville.edu), Dec 23 2008]
a(n)=(1/24)*{7*(n mod 4)-5*[(n+1) mod 4]+[(n+2) mod 4]+[(n+3) mod 4]}, with n>=0 [From Paolo P. Lava (paoloplava(AT)gmail.com), Feb 06 2009]
a(n)=(1/4)*[1-(-1)^n+I^(1+n)-I^(1-n)], with n>=0 and I=sqrt(-1) [From Paolo P. Lava (paoloplava(AT)gmail.com), May 04 2010]
a(n) = (1+(-1)^n)*(1+I^n)/4 with I=sqrt(-1). - Bruno Berselli, Mar 14 2011
a(n) = 1/4 -sin(Pi*(n-1)/2)/2+(-1)^n/4. - R. J. Mathar, Oct 08 2011
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CROSSREFS
| A121262 is another version.
Sequence in context: A111900 A157228 A105563 * A129251 A144602 A160351
Adjacent sequences: A011762 A011763 A011764 * A011766 A011767 A011768
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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