A246020 Number of palstars of length 2n over an alphabet of size 3.

1, 3, 15, 81, 435, 2349, 12681, 68499, 370023, 1998945, 10798821, 58338495, 315162657, 1702608147, 9198028791, 49690672857, 268444806483, 1450224181197, 7834572084033, 42324849273915, 228652292458773, 1235252381526711, 6673226101644267, 36050889090859101

Offset

0,2

Links

Lars Blomberg, Table of n, a(n) for n = 0..100

L. Bruce Richmond and J. Shallit, Counting the Palstars, Electronic Journal of Combinatorics, 21(3) (2014), #P3.25.

Prog

(PARI) \\ Richmond and Shallit, Section 2
U(k, size)= { local u; u= vector(size, x, 0); u[1]=1;
for (i = 1, length(u)-1, if(i%2==1, u[i+1]=k*u[i], u[i+1]=k*u[i]-u[i\2+1]));
return(u); }
u = U(3, 101);
p = vector(length(u), x, 0); p[1]=1;
for(n=1, length(u)-1, p[n+1]=sum(i=1, n, u[i+1]*p[n-i+1]));
p \\ Lars Blomberg, Jul 25 2017

Crossrefs

Cf, A246019, A246021.

Sequence in context: A229841 A198628 A233020 * A084120 A163470 A122868

Adjacent sequences: A246017 A246018 A246019 * A246021 A246022 A246023

Keyword

nonn

Author

N. J. A. Sloane, Aug 13 2014

Extensions

a(11)-a(23) from Lars Blomberg, Jul 25 2017

Status

approved