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%I #16 Sep 02 2024 17:02:20
%S 1,3,9,2889,2899999989,4899999987,19899999972,29898999693,49989958299,
%T 49999917897,99884394999,372797889885,1989767716659,2678052898989,
%U 17902896898419,137530987695297,189281899170567,368055404997498,14048104419899757,437893473401621955,218264275944702783
%N Smallest solution to gcd(k, reverse(k)) = 3^n.
%H Sean A. Irvine, <a href="/A072005/b072005.txt">Table of n, a(n) for n = 0..25</a>
%F a(n) = A069554(3^n).
%e n=4: 3^4 = 81, a(4) = 2899999989 = 3*3*3*3*35802469, reverse(a(4)) = 2*3*3*3*3*61111111; gcd = 81 = 3^n.
%Y Cf. A004086, A055483, A069554, A071686, A071686, A072021, A072050.
%K nonn,base
%O 0,2
%A _Labos Elemer_, Jun 04 2002
%E a(15)-a(20) from _Giovanni Resta_, Oct 30 2019