A295404 G.f. A(x) satisfies: A(x) = A(x)^2 - x*A(x)^3 + x^2.

1, 1, 1, 4, 10, 32, 95, 306, 978, 3235, 10767, 36470, 124514, 429648, 1492944, 5225700, 18396350, 65115694, 231555165, 826956617, 2964543205, 10664540170, 38484972969, 139281469165, 505408580484, 1838442927937, 6702466323520, 24486411113076, 89630823136513, 328680670354328, 1207323483992684, 4441801238353311, 16365832987077134, 60384021404260146, 223087697417538491

Offset

0,4

Links

Paul D. Hanna, Table of n, a(n) for n = 0..500

Formula

G.f. A(x) satisfies: A(x) = 1 + x*A(x)^2 - x^2/A(x).

a(n) ~ sqrt((s^3 - 2*r)/(Pi*(3*r*s - 1))) / (2*n^(3/2)*r^(n - 1/2)), where r = 0.2590976379022320530812109572925567785373263490686... and s = 1.89364715749587181948481325332597309754099061462... are real roots of the system of equations r^2 + s^2 = s + r*s^3, 1 + 3*r*s^2 = 2*s. - Vaclav Kotesovec, Nov 23 2017

Example

G.f.: A(x) =  1 + x + x^2 + 4*x^3 + 10*x^4 + 32*x^5 + 95*x^6 + 306*x^7 + 978*x^8 + 3235*x^9 + 10767*x^10 + 36470*x^11 + 124514*x^12 + 429648*x^13 + 1492944*x^14 + 5225700*x^15 + 18396350*x^16 + 65115694*x^17 + 231555165*x^18 + 826956617*x^19 + 2964543205*x^20 +...
such that A(x) = A(x)^2 - x*A(x)^3 + x^2.
RELATED SERIES.
1/A(x) = 1 - x - 3*x^3 - 3*x^4 - 16*x^5 - 32*x^6 - 121*x^7 - 329*x^8 - 1138*x^9 - 3546*x^10 - 12097*x^11 - 40112*x^12 +...
A(x)^2 = 1 + 2*x + 3*x^2 + 10*x^3 + 29*x^4 + 92*x^5 + 290*x^6 + 946*x^7 + 3114*x^8 + 10438*x^9 + 35332*x^10 + 120968*x^11 + 417551*x^12 +...
A(x)^3 = 1 + 3*x + 6*x^2 + 19*x^3 + 60*x^4 + 195*x^5 + 640*x^6 + 2136*x^7 + 7203*x^8 + 24565*x^9 + 84498*x^10 + 293037*x^11 + 1023184*x^12 +...
where A(x) = 1 + x*A(x)^2 - x^2/A(x).
Series_Reversion(x*A(x)) = x - x^2 + x^3 - 4*x^4 + 10*x^5 - 32*x^6 + 107*x^7 - 360*x^8 + 1270*x^9 - 4544*x^10 + 16537*x^11 - 61092*x^12 + 228084*x^13 - 860056*x^14 + 3269994*x^15 +...+ (-1)^(n-1)*A137954(n-1)*x^n +...

Prog

(PARI) {a(n)=local(A=1+x); for(i=1, n, A = 1 + x*A^2 - x^2/A  +x*O(x^n)); polcoeff(G=A, n)}
for(n=0, 40, print1(a(n), ", "))

Crossrefs

Cf. A137954.

Sequence in context: A015796 A318562 A034717 * A001673 A017936 A033297

Adjacent sequences: A295401 A295402 A295403 * A295405 A295406 A295407

Keyword

nonn

Author

Paul D. Hanna, Nov 21 2017

Status

approved