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A325906
a(n) = ( (-1)^n * Sum_{k=0..n-2} (-1)^k*10^(2^k) + 10^(2^(n-1)) - ((-1)^n+3)/2 )/9.
3
1, 12, 1121, 11112212, 1111111122221121, 11111111111111112222222211112212, 1111111111111111111111111111111122222222222222221111111122221121
OFFSET
1,2
LINKS
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
Sequence in context: A354822 A260030 A160010 * A181718 A004073 A109229
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 08 2019
STATUS
approved