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A047253 Numbers that are congruent to {1, 2, 3, 4, 5} mod 6. 19
1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 79, 80, 81, 82, 83, 85, 86 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Numbers that are not divisible by 6. - Benoit Cloitre, Jul 11 2009
More generally the sequence a(n,m) of numbers not divisible by some fixed integer m >= 2 is given by a(n,m) = n - 1 + floor((n+m-2)/(m-1)). - Benoit Cloitre, Jul 11 2009
LINKS
FORMULA
a(n) = 5 + a(n-5).
G.f.: x*(1+x)*(1+x+x^2)*(x^2-x+1) / ( (x^4+x^3+x^2+x+1)*(x-1)^2 ).
a(n) = n - 1 + floor((n+4)/5). - Benoit Cloitre, Jul 11 2009
A122841(a(n)) = 0. - Reinhard Zumkeller, Nov 10 2013
Sum_{n>=1} (-1)^(n+1)/a(n) = (15-4*sqrt(3))*Pi/36. - Amiram Eldar, Dec 31 2021
MATHEMATICA
Select[Table[n, {n, 200}], Mod[#, 6]!=0&] (* Vladimir Joseph Stephan Orlovsky, Feb 18 2011*)
PROG
(PARI) a(n)= 1+n+n\5
(PARI) a(n)=n-1+floor((n+4)/5) \\ Benoit Cloitre, Jul 11 2009
(Haskell)
a047253 n = n + n `div` 5
a047253_list = [1..5] ++ map (+ 6) a047253_list
-- Reinhard Zumkeller, Nov 10 2013
CROSSREFS
Sequence in context: A194386 A187390 A039215 * A248910 A254278 A204878
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Extended by R. J. Mathar, Oct 18 2008
STATUS
approved

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Last modified April 16 04:17 EDT 2024. Contains 371696 sequences. (Running on oeis4.)