A325906 a(n) = ( (-1)^n * Sum_{k=0..n-2} (-1)^k*10^(2^k) + 10^(2^(n-1)) - ((-1)^n+3)/2 )/9.

1, 12, 1121, 11112212, 1111111122221121, 11111111111111112222222211112212, 1111111111111111111111111111111122222222222222221111111122221121

Offset

1,2

Links

Seiichi Manyama, Table of n, a(n) for n = 1..10

Example

n |       a(n)       |    A325910(n)
--+------------------+-----------------
1 |                1 |                1
2 |               12 |               10
3 |             1121 |             1101
4 |         11112212 |         11110010
5 | 1111111122221121 | 1111111100001101

Mathematica

a[n_] := ((-1)^n * Sum[(-1)^k * 10^(2^k), {k, 0, n - 2}] + 10^(2^(n - 1)) - ((-1)^n + 3)/2)/9; Array[a, 7] (* Amiram Eldar, May 07 2021 *)

Prog

(PARI) {a(n) = ((-1)^n*sum(k=0, n-2, (-1)^k*10^2^k)+10^2^(n-1)-((-1)^n+3)/2)/9}

Crossrefs

Cf. A325907, A325910.

Sequence in context: A354822 A260030 A160010 * A181718 A004073 A109229

Adjacent sequences: A325903 A325904 A325905 * A325907 A325908 A325909

Keyword

nonn

Author

Seiichi Manyama, Sep 08 2019

Status

approved