Decimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 2,1,2.

A037575

Decimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 2,1,2.

Terms

    a(0) =2a(1) =21a(2) =212a(3) =2122a(4) =21221a(5) =212212a(6) =2122122a(7) =21221221a(8) =212212212a(9) =2122122122a(10) =21221221221a(11) =212212212212

External references