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10, 1, 2, 1, 2, 5, 2, 1, 2, 1, 10, 1, 2, 1, 2, 5, 2, 1, 2, 1, 10, 1, 2, 1, 2, 5, 2, 1, 2, 1, 10, 1, 2, 1, 2, 5, 2, 1, 2, 1, 10, 1, 2, 1, 2, 5, 2, 1, 2, 1, 10, 1, 2, 1, 2, 5, 2, 1, 2, 1, 10, 1, 2, 1, 2, 5, 2, 1, 2, 1, 10, 1, 2, 1, 2, 5, 2, 1, 2, 1, 10, 1, 2, 1, 2, 5, 2, 1, 2, 1, 10, 1, 2, 1, 2, 5, 2, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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FORMULA
| a(n) = 1 + [2|n] + 4*[5|n] + 4*[10|n], where [x|y] = 1 when x divides y, 0 otherwise.
a(n) = a(n-10).
Multiplicative with a(p^e, 10) = GCD(p^e, 10). David W. Wilson (davidwwilson(AT)comcast.net) Jun 12, 2005.
G.f. ( -10-x-2*x^2-x^3-2*x^4-5*x^5-2*x^6-x^7-2*x^8-x^9 ) / ( (x-1)*(1+x)*(x^4+x^3+x^2+x+1)*(x^4-x^3+x^2-x+1) ). - R. J. Mathar, Apr 04 2011
Dirichlet g.f. zeta(s)*(1+1/2^s+4/5^s+4/10^s). - R. J. Mathar, Apr 04 2011
a(n)= ((n-1) mod 2 + 1)*(4*floor(((n-1) mod 5)/4) + 1). [From Gary Detlefs, Dec 28 2011]
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MATHEMATICA
| GCD[Range[0, 100], 10] (* From Harvey P. Dale, Jul 11 2011 *)
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CROSSREFS
| Cf. A109004.
Sequence in context: A156767 A174921 A010180 * A085764 A090555 A010179
Adjacent sequences: A109010 A109011 A109012 * A109014 A109015 A109016
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KEYWORD
| nonn,easy,mult
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AUTHOR
| Mitch Harris (Harris.Mitchell(AT)mgh.harvard.edu)
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