1,2

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

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

Eric Weisstein's World of Mathematics, Alternating Permutations

Reinhard Zumkeller, Illustration for A074066-A074068

Index entries for sequences that are permutations of the natural numbers

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

Cf. A074066, A074068.

Sequence in context: A135155 A131184 A011263 this_sequence A110988 A047224 A127817

Adjacent sequences: A074064 A074065 A074066 this_sequence A074068 A074069 A074070

nonn

Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 17 2002