|
Search: id:A120017
|
|
| |
|
| 1, 2, 4, 10, 32, 116, 440, 1708, 6760, 27232, 111392, 461536, 1933024, 8170400, 34807232, 149304080, 644298592, 2795216576, 12184415360, 53338632256, 234393350912, 1033614750080, 4572427361536, 20285780245120, 90238113332992
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
FORMULA
|
G.f.: A(x) = (1 - sqrt(1 - 4*x*(1-x)/(1-2*x+2*x^2) ))/2.
|
|
EXAMPLE
|
A(x) = x + 2*x^2 + 4*x^3 + 10*x^4 + 32*x^5 + 116*x^6 + 440*x^7 +...
G(x) = x + x^2 + x^3 + 2*x^4 + 6*x^5 + 18*x^6 + 53*x^7 + 158*x^8 +...
where G(x) is the g.f. of A120010 and G(G(x)) = A(x).
|
|
PROGRAM
|
(PARI) {a(n)=polcoeff((1 - sqrt(1 - 4*x*(1-x)/(1-2*x+2*x^2+x*O(x^n)) ))/2, n)}
|
|
CROSSREFS
|
Cf. A120010, A120018 (3-rd self-composition).
Sequence in context: A070900 A151400 A071954 this_sequence A000736 A001250 A013032
Adjacent sequences: A120014 A120015 A120016 this_sequence A120018 A120019 A120020
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Paul D. Hanna (pauldhanna(AT)juno.com), Jun 14 2006
|
|
|
Search completed in 0.002 seconds
|
