A363308 -id:A363308 - cp's OEIS frontend

A363309 Expansion of g.f. A(x) = F(xF(x)^5), where F(x) = 1 + xF(x)^3 is the g.f. of A001764.

1, 1, 8, 67, 590, 5403, 51034, 494268, 4886794, 49153835, 501631980, 5182767291, 54115252508, 570206217940, 6055948422280, 64765311313944, 696876526961130, 7539151412082315, 81957518070961472, 894826829565106185, 9808173152466891270, 107888887505651377475

Offset: 0

Paul D. Hanna, May 29 2023

nonn

Compare the g.f. A(x) = F(x*F(x)^5) to F(-x*F(x)^5) = 1/F(x), where F(x) = 1 + x*F(x)^3 is the g.f. of A001764.

Conjecture: given A(x) = F(x*F(x)^(2*n-1)) where F(x) = 1 + x*F(x)^n, let B(x) = A(x*B(x)^(n-1)), then ((B(x) - 1)/x)^(1/(2*n-1)) is an integer series for n >= 1. Incidentally, the function A(x) = F(x*F(x)^(2*n-1)) is interesting because F(-x*F(x)^(2*n-1)) = 1/F(x) when F(x) = 1 + x*F(x)^n. This sequence illustrates the case for n = 3; for n = 2, see A363308.

			G.f.: A(x) = 1 + x + 8*x^2 + 67*x^3 + 590*x^4 + 5403*x^5 + 51034*x^6 + 494268*x^7 + 4886794*x^8 + 49153835*x^9 + 501631980*x^10 + ...
such that A(x) = F(x*F(x)^5) where F(x) = 1 + x*F(x)^3 begins
F(x) = 1 + x + 3*x^2 + 12*x^3 + 55*x^4 + 273*x^5 + 1428*x^6 + 7752*x^7 + ... + A001764(n)*x^n + ...
RELATED SERIES.
Let B(x) = A(x*B(x)^2) which begins
B(x) = 1 + x + 10*x^2 + 120*x^3 + 1620*x^4 + 23560*x^5 + 360352*x^6 + 5714800*x^7 + 93129840*x^8 + ... + A363310(n)*x^n + ...
then
( (B(x) - 1)/x )^(1/5) = 1 + 2*x + 16*x^2 + 180*x^3 + 2360*x^4 + 33760*x^5 + 510928*x^6 + 8043440*x^7 + ... + A363311(n)*x^n + ...
is an integer series.

Paul D. Hanna, Table of n, a(n) for n = 0..300

Cf. A363308, A363309, A363310, A363311, A363111, A001764.

{a(n) = if(n==0, 1, sum(k=1, n, 5*k* binomial(3*k+1, k) * binomial(3*n+2*k, n-k) / ((3*k+1)*(3*n+2*k)) ) )}
for(n=0, 30, print1(a(n), ", "))

/* G.f. A(x) = F(x*F(x)^5), where F(x) = 1 + x*F(x)^3 */
{a(n) = my(F = 1); for(i=1,n, F = 1 + x*F^3 + x*O(x^n));
polcoeff( subst(F, x, x*F^5), n)}
for(n=0, 30, print1(a(n), ", "))

G.f. A(x) = Sum_{n>=0} a(n)*x^n may be defined as follows; here, F(x) is the g.f. of A001764.
(1) A(x) = F(x*F(x)^5), where F(x) = 1 + x*F(x)^3.
(2) A(x) = B(x/A(x)^2) where B(x) = A(x*B(x)^2) = F( x*B(x)^2 * F(x*B(x)^2)^5 ) is the g.f. of A363310.
(3) a(n) = Sum_{k=1..n} 5*k* binomial(3*k+1, k) * binomial(3*n+2*k, n-k) / ((3*k+1)*(3*n+2*k)) for n > 0, with a(0) = 1.

A033296 Number of paths from (0,0) to (3n,0) that stay in first quadrant (but may touch horizontal axis), where each step is (2,1),(1,2) or (1,-1) and start with (1,2).

Original entry on oeis.org

1, 1, 6, 42, 326, 2706, 23526, 211546, 1951494, 18366882, 175674054, 1702686090, 16686795846, 165079509042, 1646340228006, 16534463822010, 167081444125702, 1697551974416706, 17330661859937670, 177699201786231530

Offset: 0

Emeric Deutsch

nonn

			G.f. A(x) = 1 + x + 6*x^2 + 42*x^3 + 326*x^4 + 2706*x^5 + 23526*x^6 + 211546*x^7 + 1951494*x^8 + 18366882*x^9 + 175674054*x^10 + ...

Cf. A027307, A032349, A363308.

/* G.f. A(x) = (1/x)*Series_Reversion( x/C(x*C(x)^3) ) */
{a(n) = my(C = (1 - sqrt(1 - 4*x +x^2*O(x^n)))/(2*x)); polcoeff( (1/x)*serreverse(x/subst(C,x,x*C^3)), n)}
for(n=0,20,print1(a(n),", ")) \\ Paul D. Hanna, May 28 2023

G.f.: A(x) = 1 + x*D(x)^3, where D(x) is the g.f. of A027307. Also: difference of A027307 and A032349. [Changed formula to include a(0) = 1. - Paul D. Hanna, May 28 2023]
D-finite with recurrence +n*(2*n+1)*a(n) +(-32*n^2+47*n-17)*a(n-1) +2*(55*n^2-223*n+228)*a(n-2) +3*(-4*n^2+33*n-70)*a(n-3) -(2*n-7)*(n-5)*a(n-4)=0. - R. J. Mathar, Jul 24 2022
From Paul D. Hanna, May 28 2023: (Start)
G.f. A(x) = (1/x) * Series_Reversion( x / C(x*C(x)^3) ), where C(x) = 1 + x*C(x)^2 is the g.f. of the Catalan numbers (A000108).
G.f. A(x) = B(x*A(x)) where B(x) = A(x/B(x)) = C(x*C(x)^3) is the g.f. of A363308, and C(x) is the g.f. of the Catalan numbers (A000108). (End)

A363111 Expansion of g.f. A(x) = F(xF(x)^7), where F(x) = 1 + xF(x)^4 is the g.f. of A002293.

Original entry on oeis.org

1, 1, 11, 127, 1547, 19652, 258069, 3481034, 47999915, 674086924, 9612919156, 138878011335, 2028718584989, 29918897595468, 444889269572286, 6663228661354420, 100430376524360459, 1522215623202615036, 23187346871707554564, 354783440893854307244

Offset: 0

Paul D. Hanna, May 30 2023

nonn

Compare the g.f. A(x) = F(x*F(x)^7) to F(-x*F(x)^7) = 1/F(x), where F(x) = 1 + x*F(x)^4 is the g.f. of A002293.

			G.f.: A(x) = 1 + x + 11*x^2 + 127*x^3 + 1547*x^4 + 19652*x^5 + 258069*x^6 + 3481034*x^7 + 47999915*x^8 + 674086924*x^9 + ...
such that A(x) = F(x*F(x)^7) where F(x) = 1 + x*F(x)^4 begins
F(x) = 1 + x + 4*x^2 + 22*x^3 + 140*x^4 + 969*x^5 + 7084*x^6 + 53820*x^7 + ... + A002293(n)*x^n + ...
RELATED SERIES.
Let B(x) = A(x*B(x)^3) = ( Series_Reversion( x/A(x)^3 )/x )^(1/3) which begins
B(x) = 1 + x + 14*x^2 + 238*x^3 + 4578*x^4 + 95130*x^5 + 2082150*x^6 + 47295990*x^7 + 1104598378*x^8 + ...
then
( (B(x) - 1)/x )^(1/7) = 1 + 2*x + 22*x^2 + 350*x^3 + 6538*x^4 + 133658*x^5 + 2895214*x^6 + 65294502*x^7 + ... + A363304(n)*x^n + ...
is an integer series.

Cf. A363304, A363308, A363309, A002293.

{a(n) = if(n==0, 1, sum(k=1, n, 7*k* binomial(4*k+1, k) * binomial(4*n+3*k, n-k) / ((4*k+1)*(4*n+3*k)) ) )}
for(n=0, 30, print1(a(n), ", "))

/* G.f. A(x) = F(x*F(x)^7), where F(x) = 1 + x*F(x)^4 */
{a(n) = my(F = 1); for(i=1,n, F = 1 + x*F^4 + x*O(x^n));
polcoeff( subst(F, x, x*F^7), n)}
for(n=0, 30, print1(a(n), ", "))

G.f. A(x) = Sum_{n>=0} a(n)*x^n may be defined as follows; here, F(x) is the g.f. of A002293.
(1) A(x) = F(x*F(x)^7), where F(x) = 1 + x*F(x)^4.
(2) A(x) = B(x/A(x)^3) where B(x) = A(x*B(x)^3) = F( x*B(x)^3 * F(x*B(x)^3)^7 ).
(3) a(n) = Sum_{k=1..n} 7*k* binomial(4*k+1, k) * binomial(4*n+3*k, n-k) / ((4*k+1)*(4*n+3*k)) for n > 0, with a(0) = 1.

cp's OEIS Frontend

A363309 Expansion of g.f. A(x) = F(xF(x)^5), where F(x) = 1 + xF(x)^3 is the g.f. of A001764.

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A033296 Number of paths from (0,0) to (3n,0) that stay in first quadrant (but may touch horizontal axis), where each step is (2,1),(1,2) or (1,-1) and start with (1,2).

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A363111 Expansion of g.f. A(x) = F(xF(x)^7), where F(x) = 1 + xF(x)^4 is the g.f. of A002293.

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cp's OEIS Frontend

A363309 Expansion of g.f. A(x) = F(x*F(x)^5), where F(x) = 1 + x*F(x)^3 is the g.f. of A001764.

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PARI

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A033296 Number of paths from (0,0) to (3n,0) that stay in first quadrant (but may touch horizontal axis), where each step is (2,1),(1,2) or (1,-1) and start with (1,2).

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A363111 Expansion of g.f. A(x) = F(x*F(x)^7), where F(x) = 1 + x*F(x)^4 is the g.f. of A002293.

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A363309 Expansion of g.f. A(x) = F(xF(x)^5), where F(x) = 1 + xF(x)^3 is the g.f. of A001764.

A363111 Expansion of g.f. A(x) = F(xF(x)^7), where F(x) = 1 + xF(x)^4 is the g.f. of A002293.