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%I #11 Jul 10 2020 11:38:32
%S 0,1,0,1,1,1,1,0,0,0,1,0,1,1,1,0,1,0,0,1,0,0,1,0,1,0,0,0,1,0,0,1,1,0,
%T 0,0,1,1,1,0,1,0,1,1,1,1,0,1,1,1,0,0,0,1,1,0,1,0,1,0,1,0,1,0,1,1,0,0,
%U 0,0,1,1,1,0,1,1,0,0,1,0,1,0,1,0,1,1,1
%N Digits of the 2-adic integer arctanh(2).
%C arctanh(x) = x + x^3/3 + x^5/5 + x^7/7 + ...
%H Robert Israel, <a href="/A309754/b309754.txt">Table of n, a(n) for n = 0..2500</a>
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/P-adic_number">p-adic number</a>
%F a(n) = (A309753(n+1) - A309753(n))/2^n.
%e arctanh(2) = ...0111000110010001010010010111010001111010.
%p N:= 100: # for a(0)..a(N)
%p T:= 0:
%p for k from 1 to N by 2 do
%p T:= padic:-evalp(T + 2^k/k, 2, N+1)
%p od:
%p 0, op(op([1,3],T)); # _Robert Israel_, Jul 10 2020
%o (PARI) a(n) = lift(sum(i=0, (n-1)/2, Mod(2^(2*i+1)/(2*i+1), 2^(n+1))))\2^n
%Y Cf. A309752, A309753.
%K nonn,base
%O 0
%A _Jianing Song_, Aug 15 2019
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