|
Search: id:A087224
|
|
|
| A087224 |
|
G.f. satisfies A(x) = f(x)^2 + x*A(x)*f(x)^3, where f(x)=sum(k>=0,x^((4^n-1)/3)). |
|
+0
4
|
|
| 1, 3, 7, 19, 50, 133, 352, 935, 2482, 6584, 17473, 46365, 123034, 326478, 866338, 2298895, 6100296, 16187616, 42955106, 113984740, 302467434, 802621041, 2129817812, 5651638433, 14997065388, 39795888008, 105601506802
(list; graph; listen)
|
|
|
OFFSET
|
0,2
|
|
|
FORMULA
|
a(n) = A087221(3n+2).
|
|
EXAMPLE
|
Given f(x) = 1 +x +x^5 +x^21 +x^85 +x^341 +...
so that f(x)^2 = 1 +2x +x^2 +2x^5 +2x^6 +x^10 +2x^21 +...
and f(x)^3 = 1 +3x +3x^2 +x^3 +3x^5 +6x^6 +3x^7 +3x^10 +...
then A(x) = (1+2x+x^2+2x^5+...) + x*A(x)*(1+3x+3x^2+x^3+3x^5+...)
= 1 +3x +7x^2 +19x^3 +50x^4 +133x^5 +352x^6 +...
|
|
PROGRAM
|
(PARI) a(n)=local(A, m); if(n<1, n==0, m=1; A=1+O(x); while(m<=3*n+3, m*=4; A=1/(1/subst(A, x, x^4)-x)); polcoeff(A, 3*n+2))
|
|
CROSSREFS
|
Cf. A087221, A087222, A087223.
Sequence in context: A116903 A151266 A147234 this_sequence A078059 A018031 A052948
Adjacent sequences: A087221 A087222 A087223 this_sequence A087225 A087226 A087227
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Paul D. Hanna (pauldhanna(AT)juno.com), Aug 27 2003
|
|
|
Search completed in 0.002 seconds
|
