A327612 Number of length n reversible string structures that are not palindromic using any number of colors.

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

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