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A122088
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Add 10, subtract 5, add 10, subtract 5, ad infinitum.
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0
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1, 11, 6, 16, 11, 21, 16, 26, 21, 31, 26, 36, 31, 41, 36, 46, 41, 51, 46, 56, 51, 61, 56, 66, 61, 71, 66, 76, 71, 81, 76, 86, 81, 91, 86, 96, 91, 101, 96, 106, 101, 111, 106, 116, 111, 121, 116, 126, 121, 131, 126, 136, 131, 141, 136, 146, 141, 151, 146, 156, 151, 161, 156, 166, 161, 171
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| A brain teaser.
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LINKS
| Math. Central U. Regina, no. 377 of QQ03
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FORMULA
| a(2j+1) = 5j+1, a(2j) = 5j+6. - Robert G. Wilson v (rgwv(AT)rgwv.com), Nov 26 2006, R. J. Mathar, Jul 09 2009
G.f.: x*(1+10*x-6*x^2)/((1+x)*(1-x)^2). a(n)=9/4+5*n/2+15*(-1)^n/4. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 09 2009
a(n+1)=(5/2)*[1+3*(-1)^n]+a(n), with a(1)=1 [From Paolo P. Lava (paoloplava(AT)gmail.com), Jul 21 2009]
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CROSSREFS
| Sequence in context: A080501 A122098 A115943 * A190624 A038320 A010185
Adjacent sequences: A122085 A122086 A122087 * A122089 A122090 A122091
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KEYWORD
| nonn,easy
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AUTHOR
| Chris H. (chrishale(AT)deotte.com), Oct 17 2006
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EXTENSIONS
| Present definition supplied by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 20 2006
More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Nov 26 2006
Formulas adapted to offset by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 09 2009
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