1,2

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

for n>1: a(n) = n iff n == 0 modulo 7.

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) = 7*floor(n/7) + 14*floor((n mod 7)/4) - (n mod 7) for n>3; a(n)=n for n<=3.

Cf. A074066, A074067.

Sequence in context: A128531 A123167 A141670 this_sequence A055655 A007090 A102859

Adjacent sequences: A074065 A074066 A074067 this_sequence A074069 A074070 A074071

nonn

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