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A047201
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Numbers that are congruent to {1, 2, 3, 4} mod 5.
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25
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1, 2, 3, 4, 6, 7, 8, 9, 11, 12, 13, 14, 16, 17, 18, 19, 21, 22, 23, 24, 26, 27, 28, 29, 31, 32, 33, 34, 36, 37, 38, 39, 41, 42, 43, 44, 46, 47, 48, 49, 51, 52, 53, 54, 56, 57, 58, 59, 61, 62, 63, 64, 66, 67, 68, 69, 71
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Numbers not divisible by 5. - Lekraj Beedassy (blekraj(AT)yahoo.com), Dec 17 2006
More generally the sequence of numbers not divisible by some fixed integer m>=2 is given by a(n,m)=n-1+floor((n+m-2)/(m-1)). [From Benoit Cloitre (benoit7848c(AT)orange.fr), Jul 11 2009]
Complement of A008587; A011558(a(n))=1; A079998(a(n))=0. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Nov 30 2009]
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (1,0,0,1,-1).
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
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FORMULA
| G.f.: (x+2*x^2+3*x^3+4*x^4+4*x^5+3*x^6+2*x^7+x^8)/(1-x^4)^2 (not reduced) - Len Smiley (smiley(AT)math.uaa.alaska.edu)
a(n)=5+a(n-4).
G.f.: x*(1+x+x^2+x^3+x^4)/((1-x)*(1-x^4)).
a(n)=n-1+floor((n+3)/4) [From Benoit Cloitre (benoit7848c(AT)orange.fr), Jul 11 2009]
a(n)= floor((15n-1)/12) [From Gary Detlefs (gdetlefs(AT)aol.com), Mar 07 2010]
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EXAMPLE
| seq(floor((15*n-1)/12), n= 1..56); [From Gary Detlefs (gdetlefs(AT)aol.com), Mar 07 2010]
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MATHEMATICA
| Select[Table[n, {n, 200}], Mod[#, 5]!=0&] (*From Vladimir Joseph Stephan Orlovsky, Feb 18 2011*)
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PROG
| (PARI) a(n)= 1+n+n\4
(Other) [i for i in range(72) if gcd(5, i) == 1] [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Apr 21 2009]
(PARI) a(n)=n-1+floor((n+3)/4) [From Benoit Cloitre (benoit7848c(AT)orange.fr), Jul 11 2009]
(Haskell)
a047201 n = a047201_list !! (n-1)
a047201_list = [x | x <- [1..], mod x 5 > 0]
-- Reinhard Zumkeller, Dec 17 2011
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CROSSREFS
| Cf. A045572.
Sequence in context: A001961 A020656 A039116 * A023721 A087066 A120518
Adjacent sequences: A047198 A047199 A047200 * A047202 A047203 A047204
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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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