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A246020 Number of palstars of length 2n over an alphabet of size 3. 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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified August 23 00:50 EDT 2019. Contains 326211 sequences. (Running on oeis4.)