OFFSET
1,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..500
EXAMPLE
a(1) = 1: B.
a(2) = 4: B(B), B(W), W(B).
a(3) = 9: B(BB), B(BW), B(WW), W(BB), B(B(B)), B(B(W)), B(W(B)), W(B(B)), W(B(W)).
PROG
(PARI) EulerT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v, n, 1/n))))-1, -#v)}
seq(n)={my(u=v=w=[]); for(n=1, n, my(t1=EulerT(v), t2=EulerT(u+v)); u=concat([1], EulerT(u+v+w)); v=concat([0], t2-t1); w=concat([1], t1)); u+v}
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Dec 19 2020
STATUS
approved