

A074067


Zigzag modulo 5.


3



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, 23, 32, 31, 30, 29, 28, 37, 36, 35, 34, 33, 42, 41, 40, 39, 38, 47, 46, 45, 44, 43, 52, 51, 50, 49, 48, 57, 56, 55, 54, 53, 62, 61, 60, 59, 58, 67, 66, 65, 64, 63, 72, 71
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OFFSET

1,2


COMMENTS

a(a(n))=n (a selfinverse permutation);
for n>1: a(n) = n iff n == 0 modulo 5.


LINKS

Table of n, a(n) for n=1..69.
Eric Weisstein's World of Mathematics, Alternating Permutations
Reinhard Zumkeller, Illustration for A074066A074068
Index entries for sequences that are permutations of the natural numbers


FORMULA

a(n) = 5*floor(n/5) + 10*floor((n mod 5)/3)  (n mod 5) for n>2; a(n)=n for n<=2.
a(n) = a(n1) + a(n5)  a(n6) for n > 8.  Chai Wah Wu, May 25 2016


MATHEMATICA

{1, 2}~Join~Flatten[Reverse /@ Partition[Range[3, 72], 5]] (* after Harvey P. Dale at A074066, or *)
{1, 2}~Join~Table[5 Floor[n/5] + 10 Floor[#/3]  # &@ Mod[n, 5], {n, 3, 69}] (* Michael De Vlieger, May 25 2016 *)


PROG

(Haskell)
a074067 n = a074067_list !! (n1)
a074067_list = 1 : 2 : xs where xs = 7 : 6 : 5 : 4 : 3 : map (+ 5) xs
 Reinhard Zumkeller, Feb 21 2011


CROSSREFS

Cf. A074066, A074068.
Sequence in context: A244847 A175477 A011263 * A110988 A047224 A127817
Adjacent sequences: A074064 A074065 A074066 * A074068 A074069 A074070


KEYWORD

nonn


AUTHOR

Reinhard Zumkeller, Aug 17 2002


STATUS

approved



