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 A074067 Zigzag modulo 5. 3

%I

%S 1,2,7,6,5,4,3,12,11,10,9,8,17,16,15,14,13,22,21,20,19,18,27,26,25,24,

%T 23,32,31,30,29,28,37,36,35,34,33,42,41,40,39,38,47,46,45,44,43,52,51,

%U 50,49,48,57,56,55,54,53,62,61,60,59,58,67,66,65,64,63,72,71

%N Zigzag modulo 5.

%C a(a(n))=n (a self-inverse permutation);

%C for n>1: a(n) = n iff n == 0 modulo 5.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/AlternatingPermutation.html">Alternating Permutations</a>

%H Reinhard Zumkeller, <a href="/A074066/a074066.ps">Illustration for A074066-A074068</a>

%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>

%F a(n) = 5*floor(n/5) + 10*floor((n mod 5)/3) - (n mod 5) for n>2; a(n)=n for n<=2.

%F a(n) = a(n-1) + a(n-5) - a(n-6) for n > 8. - _Chai Wah Wu_, May 25 2016

%t {1, 2}~Join~Flatten[Reverse /@ Partition[Range[3, 72], 5]] (* after _Harvey P. Dale_ at A074066, or *)

%t {1, 2}~Join~Table[5 Floor[n/5] + 10 Floor[#/3] - # &@ Mod[n, 5], {n, 3, 69}] (* _Michael De Vlieger_, May 25 2016 *)

%o a074067 n = a074067_list !! (n-1)

%o a074067_list = 1 : 2 : xs where xs = 7 : 6 : 5 : 4 : 3 : map (+ 5) xs

%o -- _Reinhard Zumkeller_, Feb 21 2011

%Y Cf. A074066, A074068.

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Aug 17 2002

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Last modified February 17 10:59 EST 2019. Contains 320219 sequences. (Running on oeis4.)