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A246021 Number of palstars of length 2n over an alphabet of size 4. 3
1, 4, 28, 208, 1540, 11440, 84976, 631360, 4690972, 34854352, 258971536, 1924189120, 14296956112, 106228114624, 789287772352, 5864503926016, 43573975930372, 323759929988272, 2405575577105392, 17873718523387456, 132803898120114352, 986749082625941824 (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(4, 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, A246020.

Sequence in context: A270471 A019482 A198630 * A090965 A106258 A085363

Adjacent sequences:  A246018 A246019 A246020 * A246022 A246023 A246024

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Aug 13 2014

EXTENSIONS

a(11)-a(21) from Lars Blomberg, Jul 25 2017

STATUS

approved

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Last modified August 19 18:51 EDT 2019. Contains 326133 sequences. (Running on oeis4.)