1,2

Carole Dubois, Table of n, a(n) for n = 1..5001

a(1) + a(2) = 1 + 10 = 11 (a pair of 1's);

a(2) + a(3) = 10 + 12 = 22 (a pair of 2's);

a(3) + a(4) = 12 + 21 = 33 (a pair of 3's);

...

a(10) + a(11) = 54 + 46 = 100 (a pair of 0's); etc.

Cf. A043096 (numbers in which every pair of adjacent digits are distinct).

Sequence in context: A035284 A265403 A215940 * A320170 A082927 A108965

Adjacent sequences: A337863 A337864 A337865 * A337867 A337868 A337869

nonn,base

Eric Angelini and Carole Dubois, Sep 27 2020

approved