%I
%S 0,1,21,71,196,2071,2071,33321,345821,736446,8548946,18314571,
%T 18314571,994877071,994877071,25408939571,86444095821,239031986446,
%U 1001971439571,16260760502071,92554705814571,283289569095821,1236963885502071,8389521258548946
%N Approximation of the 5adic integer exp(5) up to 5^n.
%C In padic field, the exponential function exp(x) is defined as Sum_{k>=0} x^k/k!. When extended to a function over the metric completion of the padic field, exp(x) has radius of convergence p^(1/(p1)) (i.e., exp(x) converges for x such that x_p < p^(1/(p1)), where x_p is the padic metric). As a result, for odd primes p, exp(p) is welldefined in padic field, and exp(4) is well defined in 2adic field.
%C a(n) is the multiplicative inverse of A309902(n) modulo 5^n.
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Padic_number">padic number</a>
%o (PARI) a(n) = lift(exp(5 + O(5^n)))
%Y Cf. A309902.
%Y The 5adic expansion of exp(5) is given by A309975.
%Y Approximations of exp(p) in padic field: A309901 (p=3), this sequence (p=5), A309905 (p=7).
%K nonn
%O 0,3
%A _Jianing Song_, Aug 21 2019
