%I #5 Nov 18 2018 10:04:26
%S 1,0,1,0,0,0,0,1,1,1,1,1,1,0,1,1,0,1,1,1,0,0,0,0,1,0,1,0,0,1,0,0,1,0,
%T 0,0,0,1,1,0,0,1,1,0,1,0,1,1,0,1,1,0,1,0,1,0,1,0,1,0,1,1,0,0,1,0,1,1,
%U 0,1,1,1,1,1,1,1,1,1,1,0,0,1,1,1,1,0,0
%N Digits of the 2-adic integer exp(-4).
%C This is the multiplicative inverse of A320815.
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/P-adic_number">p-adic number</a>
%F a(n) = (A321689(n+1) - A321689(n))/2^n.
%e exp(-4) = ...00110000100100101000011101101111110000101.
%o (PARI) a(n) = lift(sum(i=0, n-(n>=2), Mod(4^i/i!, 2^(n+1))))\2^n
%o (PARI) a(n) = lift(exp(-4 + O(2^(n+1))))\2^n;
%Y Cf. A320815, A321689.
%K nonn,base
%O 0,1
%A _Jianing Song_, Nov 17 2018