OFFSET

0,2

EXAMPLE

The sets of numbers obtainable at the n-th step are:

S(0) = { 1 },

S(1) = { 0, 1, 2 },

S(2) = { -1, 0, 1/2, 1, 2, 3, 4 },

S(3) = { -3, -2, -3/2, -1, -1/2, 0, 1/4, 1/3, 1/2, 2/3, 1, 3/2, 2, 5/2, 3, 4, 5, 6, 8, 9, 16 }.

CROSSREFS

KEYWORD

nonn,hard,more

AUTHOR

Hugo Pfoertner, Jun 18 2017

EXTENSIONS

a(7) from Alois P. Heinz, Jun 18 2017

STATUS

approved