OFFSET
0,2
FORMULA
G.f. C(x) and related series A(x) and B(x) satisfy:
(1a) A(x) = 1/((1 - x*B(x)^2)*(1 - x*C(x)^3)),
(1b) B(x) = 1/((1 - x*A(x))*(1 - x*C(x)^3)),
(1c) C(x) = 1/((1 - x*A(x))*(1 - x*B(x)^2)).
(2a) A(x) = B(x)*C(x) * (1 - x*A(x))^2,
(2b) B(x) = A(x)*C(x) * (1 - x*B(x)^2)^2,
(2c) C(x) = A(x)*B(x) * (1 - x*C(x)^3)^2.
(3a) A(x)/(1 - x*A(x)) = B(x)/(1 - x*B(x)^2) = C(x)/(1 - x*C(x)^3) = sqrt(A(x)*B(x)*C(x)),
(3b) A(x)*B(x)*C(x) = 1/((1-x*A(x))^2*(1-x*B(x)^2)^2*(1-x*C(x)^3)^2).
EXAMPLE
G.f.: C(x) = 1 + 2*x + 9*x^2 + 61*x^3 + 489*x^4 + 4283*x^5 + 39702*x^6 + 382899*x^7 + 3802403*x^8 + 38618535*x^9 + 399277260*x^10 + ...
such that B(x) = 1/((1 - x*A(x))*(1 - x*C(x)^3)) where
A(x) = 1 + 2*x + 13*x^2 + 99*x^3 + 839*x^4 + 7606*x^5 + 72190*x^6 + 708294*x^7 + 7126305*x^8 + 73125017*x^9 + 762337935*x^10 + ...
B(x) = 1 + 2*x + 11*x^2 + 80*x^3 + 659*x^4 + 5865*x^5 + 54954*x^6 + 534087*x^7 + 5334509*x^8 + 54423368*x^9 + 564713959*x^10 + ...
RELATED SERIES.
A(x)*B(x)*C(x) = 1 + 6*x + 45*x^2 + 380*x^3 + 3438*x^4 + 32584*x^5 + 319358*x^6 + 3210482*x^7 + 32921947*x^8 + 343030506*x^9 + ...
sqrt(A(x)*B(x)*C(x)) = 1 + 3*x + 18*x^2 + 136*x^3 + 1149*x^4 + 10397*x^5 + 98558*x^6 + 966157*x^7 + 9714366*x^8 + 99631288*x^9 + ...
where
sqrt(A(x)*B(x)*C(x)) = A(x)/(1-x*A(x)) = B(x)/(1-x*B(x)^2) = C(x)/(1-x*C(x)^3).
A(x)^2 = 1 + 4*x + 30*x^2 + 250*x^3 + 2243*x^4 + 21142*x^5 + 206419*x^6 + 2069226*x^7 + 21172635*x^8 + 220227386*x^9 + ...
B(x)^2 = 1 + 4*x + 26*x^2 + 204*x^3 + 1759*x^4 + 16126*x^5 + 154266*x^6 + 1522460*x^7 + 15387035*x^8 + 158457396*x^9 + ...
C(x)^2 = 1 + 4*x + 22*x^2 + 158*x^3 + 1303*x^4 + 11620*x^5 + 109059*x^6 + 1061358*x^7 + 10612685*x^8 + 108371282*x^9 + ...
C(x)^3 = 1 + 6*x + 39*x^2 + 299*x^3 + 2550*x^4 + 23229*x^5 + 221256*x^6 + 2176734*x^7 + 21947076*x^8 + 225589243*x^9 + ...
PROG
(PARI) {a(n) = my(A=1, B=1, C=1); for(i=1, n,
A = 1/((1-x*B^2)*(1-x*C^3) +x*O(x^n));
B = 1/((1-x*A^1)*(1-x*C^3) +x*O(x^n));
C = 1/((1-x*A^1)*(1-x*B^2) +x*O(x^n)); );
polcoeff(C, n)}
for(n=0, 20, print1(a(n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Feb 25 2021
STATUS
approved