A177395 G.f. satisfies: x = A(x) - A(A(x))^2 - A(A(A(x)))^3.
1, 1, 5, 37, 338, 3530, 40546, 500781, 6556080, 90097535, 1290778689, 19180015667, 294460699563, 4656776745569, 75682133890995, 1261603117268148, 21537605020132685, 376060923637721700, 6708681746445946648
Offset: 1
Keywords
Examples
G.f.: A(x) = x + x^2 + 5*x^3 + 37*x^4 + 338*x^5 + 3530*x^6 +...
Coefficients in the iterations A_{n}(x), n=1..9, of A(x) begin:
A_1: [1, 1, 5, 37, 338, 3530, 40546, 500781, ...];
A_2: [1, 2, 12, 100, 998, 11197, 136682, 1780674, ...];
A_3: [1, 3, 21, 195, 2120, 25571, 332664, 4589974, ...];
A_4: [1, 4, 32, 328, 3868, 50078, 694340, 10157760, ...];
A_5: [1, 5, 45, 505, 6430, 89120, 1315126, 20388639, ...];
A_6: [1, 6, 60, 732, 10018, 148195, 2322702, 38106722, ...];
A_7: [1, 7, 77, 1015, 14868, 234017, 3886428, 67351872, ...];
A_8: [1, 8, 96, 1360, 21240, 354636, 6225480, 113733264, ...];
A_9: [1, 9, 117, 1773, 29418, 519558, 9617706, 184845297,...].
Coefficients in functions: x = A(x) - A_2(x)^2 - A_3(x)^3 begin:
(A_1)^1: [1, 1, 5, 37, 338, 3530, 40546, 500781, 6556080, ...];
(A_2)^2: [0, 1, 4, 28, 248, 2540, 28786, 352104, 4576404 ...];
(A_3)^3: [0, 0, 1,. 9,. 90,. 990, 11760, 148677, 1979676, ...].
Coefficients in functions: A(x) = A_2(x) - A_3(x)^2 - A_4(x)^3 begin:
(A_2)^1: [1, 2, 12, 100, 998, 11197, 136682, 1780674, 24453430, ...];
(A_3)^2: [0, 1,. 6,. 51, 516,. 5851,. 72052,. 945819, 13076714, ...];
(A_4)^3: [0, 0,. 1,. 12, 144,. 1816,. 24084,. 334074,. 4820636, ...].
Coefficients in functions: A_2(x) = A_3(x) - A_4(x)^2 -A_5(x)^3 begin:
(A_3)^1: [1, 3, 21, 195, 2120, 25571, 332664, 4589974, 66441348, ...];
(A_4)^2: [0, 1,. 8,. 80,. 912, 11384, 152092, 2144440, 31612640, ...];
(A_5)^3: [0, 0,. 1,. 15,. 210,. 2990,. 43890,. 664860, 10375278, ...].
Links
- Paul D. Hanna, Table of n, a(n), n= 1..100.
Programs
-
PARI
{a(n)=local(A=x); if(n<1, 0, for(i=1, n, A=serreverse(x-(A+x*O(x^n))^2-subst(A,x,A+x*O(x^n))^3)); polcoeff(A, n))}
Formula
G.f. satisfies: x = A( x - A(x)^2 - A(A(x))^3 ).
...
G.f. satisfies: A_{n}(x) = A_{n+1}(x) - A_{n+2}(x)^2 - A_{n+3}(x)^3 where A_{n+1}(x) = A_{n}(A(x)) denotes iteration with A_0(x)=x.
...
Given g.f. A(x), A(x)/x is the unique solution to variable A in the infinite system of simultaneous equations starting with:
. A = 1 + xB^2 + x^2*C^3;
. B = A + xC^2 + x^2*D^3;
. C = B + xD^2 + x^2*E^3;
. D = C + xE^2 + x^2*F^3; ...
. also B = A(A(x))/x, C = A(A(A(x)))/x, D = A(A(A(A(x))))/x, etc.
Extensions
Typos in examples corrected by Paul D. Hanna, May 29 2010
Formula corrected by Paul D. Hanna, May 29 2010