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a(1) = 3, a(n) = smallest nontrivial palindromic multiple of a(n-1). a(n) is not equal to a(n-1) or a concatenation of a(n-1) with itself.
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%I #10 Aug 11 2024 14:41:34

%S 3,6,222,444,888,21312,42624,468864,40322304,80644608,802494494208,

%T 213525880454088525312,213525880454088738837880454088525312

%N a(1) = 3, a(n) = smallest nontrivial palindromic multiple of a(n-1). a(n) is not equal to a(n-1) or a concatenation of a(n-1) with itself.

%C Multiplier for a(12) is larger than 2000000000.

%H P. De Geest, <a href="https://www.worldofnumbers.com/em36.htm">WONplate 36</a>

%Y Cf. A083150, A068665, A083147, A083151, A083153, A083155.

%K nonn,base,more

%O 1,1

%A _Amarnath Murthy_ and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Apr 25 2003

%E More terms from _Patrick De Geest_, Jun 05 2003

%E a(13) from _Giovanni Resta_, Sep 22 2019