cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A325910 a(n) = ( (-1)^(n-1) * Sum_{k=0..n-1} (-1)^k*10^(2^k) - (1-(-1)^n)/2 )/9.

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%I A325910 #36 May 07 2021 05:09:20
%S A325910 0,1,10,1101,11110010,1111111100001101,
%T A325910 11111111111111110000000011110010,
%U A325910 1111111111111111111111111111111100000000000000001111111100001101
%N A325910 a(n) = ( (-1)^(n-1) * Sum_{k=0..n-1} (-1)^k*10^(2^k) - (1-(-1)^n)/2 )/9.
%H A325910 Seiichi Manyama, <a href="/A325910/b325910.txt">Table of n, a(n) for n = 0..10</a>
%F A325910 a(n) = -a(n-1) + (10^(2^(n-1)) - 1)/9.
%F A325910 a(n) = A007088(A325912(n-1) - (n mod 2)) for n > 0.
%e A325910                1 =        -0 +                1.
%e A325910               10 =        -1 +               11.
%e A325910             1101 =       -10 +             1111.
%e A325910         11110010 =     -1101 +         11111111.
%e A325910 1111111100001101 = -11110010 + 1111111111111111.
%e A325910 ================================================
%e A325910 n |           (a(n))_2           | A325912(n-1)
%e A325910 --+------------------------------+-------------
%e A325910 1 |                 1    =     1 |            2
%e A325910 2 |               (10)_2 =     2 |            2
%e A325910 3 |             (1101)_2 =    13 |           14
%e A325910 4 |         (11110010)_2 =   242 |          242
%e A325910 5 | (1111111100001101)_2 = 65293 |        65294
%t A325910 a[n_] := ((-1)^(n - 1) * Sum[(-1)^k * 10^(2^k), {k, 0, n - 1} ] - (1 - (-1)^n)/2)/9; Array[a, 8, 0] (* _Amiram Eldar_, May 07 2021 *)
%o A325910 (PARI) {a(n) = ((-1)^(n-1)*sum(k=0, n-1, (-1)^k*10^2^k)-(1-(-1)^n)/2)/9}
%Y A325910 Cf. A002275, A007088, A325906, A325912.
%K A325910 nonn
%O A325910 0,3
%A A325910 _Seiichi Manyama_, Sep 08 2019