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%I #11 Apr 08 2013 11:20:17
%S 9,49,249,1249,81249,781249,5781249,25781249,425781249,6425781249,
%T 36425781249,836425781249,9836425781249,19836425781249,
%U 519836425781249,2519836425781249,12519836425781249,512519836425781249,4512519836425781249,84512519836425781249
%N (2*5^(2^n) - 1) mod 10^n: a sequence of trimorphic numbers ending in 9.
%C a(n) is the unique positive integer less than 10^n such that a(n) - 1 is divisible by 2^n and a(n) + 1 is divisible by 5^n.
%H Eric M. Schmidt, <a href="/A224473/b224473.txt">Table of n, a(n) for n = 1..1000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/TrimorphicNumber.html">Trimorphic Number</a>
%H <a href="/index/Ar#automorphic">Index entries for sequences related to automorphic numbers</a>
%F a(n) = (2 * A007185(n) - 1) mod 10^n.
%o (Sage) def A224473(n) : return crt(1, -1, 2^n, 5^n);
%Y Cf. A033819. Corresponding 10-adic number is A091661. The other trimorphic numbers ending in 9 are included in A002283, A198971 and A224475.
%K nonn,base
%O 1,1
%A _Eric M. Schmidt_, Apr 07 2013
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