A028359 Two-bell analog of A028355.

1, 2, 12, 121, 212, 1212, 12121, 21212, 121212, 1212121, 2121212, 12121212, 121212121, 212121212, 1212121212, 12121212121, 21212121212, 121212121212, 1212121212121, 2121212121212, 12121212121212, 121212121212121, 212121212121212, 1212121212121212, 12121212121212121

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• base

Comments

Consider the infinite digits: 121212... . We can break this into a sequence of integers such that the sum of digits in the n-th value is n. - Seiichi Manyama, Oct 31 2018

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..1500

Crossrefs

Cf. A000034, A028355.

Formula

Conjectures from Chai Wah Wu, Apr 18 2024: (Start)

a(n) = 101*a(n-3) - 100*a(n-6) for n > 6.

G.f.: x*(10*x^4 + 20*x^3 + 12*x^2 + 2*x + 1)/(100*x^6 - 101*x^3 + 1). (End)

Extensions

More terms from Seiichi Manyama, Oct 31 2018