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Number of periodic palindromic structures of length n using an infinite alphabet.
3

%I #13 Oct 02 2019 12:06:38

%S 1,1,2,2,5,5,13,15,41,52,144,203,578,877,2605,4140,12869,21147,69178,

%T 115975,398766,678570,2450406,4213597,15939952,27644437,109304914,

%U 190899322,787016238,1382958545,5931824093,10480142147,46673259309,82864869804,382473282504

%N Number of periodic palindromic structures of length n using an infinite alphabet.

%C See A285012 for additional information. Permuting the symbols will not change the structure.

%H Andrew Howroyd, <a href="/A285013/b285013.txt">Table of n, a(n) for n = 0..500</a>

%o (PARI) \\ Requires T from A285012.

%o seq(n)={my(A=T(n)); concat([1], vector(n, i, vecsum(A[i,])))} \\ _Andrew Howroyd_, Oct 02 2019

%Y Row sums of A285012.

%Y Cf. A165137, A284841, A285042.

%K nonn

%O 0,3

%A _Andrew Howroyd_, Apr 07 2017

%E a(0)=1 prepended and terms a(28) and beyond from _Andrew Howroyd_, Oct 02 2019