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 A327612 Number of length n reversible string structures that are not palindromic using any number of colors. 2
 0, 1, 2, 9, 27, 112, 453, 2137, 10691, 58435, 340187, 2110016, 13829358, 95474679, 691538954, 5240280999, 41432965441, 341040295916, 2916376121375, 25862097370783, 237434958512487, 2253358056604465, 22076003464423853, 222979436686398848, 2319295172150784296 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Andrew Howroyd, Table of n, a(n) for n = 1..200 FORMULA a(n) = A103293(n + 1) - A188164(n). PROG (PARI) \\ Ach is A304972 as square matrix. Ach(n)={my(M=matrix(n, n, i, k, i>=k)); for(i=3, n, for(k=2, n, M[i, k]=k*M[i-2, k] + M[i-2, k-1] + if(k>2, M[i-2, k-2]))); M} seq(n)={my(A=Ach(n)); vector(n, i, sum(k=1, n, (A[i, k] + stirling(i, k, 2))/2 - stirling((i+1)\2, k, 2)))} CROSSREFS Row sums of A309748(n > 1). Cf. A103293, A188164, A304972. Sequence in context: A277240 A256233 A123904 * A019065 A115186 A243560 Adjacent sequences:  A327609 A327610 A327611 * A327613 A327614 A327615 KEYWORD nonn AUTHOR Andrew Howroyd, Sep 18 2019 STATUS approved

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Last modified June 20 06:23 EDT 2021. Contains 345157 sequences. (Running on oeis4.)