login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A304193 G.f. A(x) satisfies: [x^n] (1+x)^((n+1)^2) / A(x) = 0 for n>0. 8
1, 4, 16, 144, 2346, 55236, 1688084, 63040736, 2770165274, 139623836116, 7925496107656, 499719554537584, 34625595715906866, 2613946666882042164, 213475621178226876156, 18748792440158256161216, 1761875767691411063734514, 176383456081424163875684516, 18739798321516251204837796864, 2105891800817103192582808107856 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Note that: [x^n] (1+x)^((n+1)*k) / G(x) = 0 for n>0 holds when G(x) = (1+x)^(k+1)/(1 - (k-1)*x) given some fixed k ; this sequence explores the case where k varies with n.

LINKS

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

FORMULA

A132618(n+1) = [x^n] (1+x)^((n+2)^2) / A(x) for n>=0.

EXAMPLE

G.f.: A(x) = 1 + 4*x + 16*x^2 + 144*x^3 + 2346*x^4 + 55236*x^5 + 1688084*x^6 + 63040736*x^7 + 2770165274*x^8 + 139623836116*x^9 + ...

ILLUSTRATION OF DEFINITION.

The table of coefficients of x^k in (1+x)^((n+1)^2) / A(x) begins:

n=0: [1, -3, -4, -80, -1530, -40222, -1316104, -51439572, ...];

n=1: [1, 0, -10, -100, -1785, -45056, -1441440, -55510080, ...];

n=2: [1, 5, 0, -140, -2380, -55080, -1685620, -63186200, ...];

n=3: [1, 12, 56, 0, -3150, -74484, -2125948, -76230384, ...];

n=4: [1, 21, 200, 1020, 0, -96492, -2901052, -98301840, ...];

n=5: [1, 32, 486, 4540, 26015, 0, -3718000, -135081440, ...];

n=6: [1, 45, 980, 13640, 132810, 855478, 0, -172046940, ...];

n=7: [1, 60, 1760, 33520, 462150, 4790156, 34461260, 0, ...]; ...

in which the main diagonal is all zeros after the initial term, illustrating that [x^n] (1+x)^((n+1)^2) / A(x) = 0 for n>0.

RELATED SEQUENCES.

The secondary diagonal in the above table that begins

[1, 5, 56, 1020, 26015, 855478, 34461260, 1642995124, ...]

yields A132618, column 2 of triangle A132615.

Related triangular matrix T = A132615 begins:

1;

1, 1;

1, 1, 1;

6, 3, 1, 1;

80, 25, 5, 1, 1;

1666, 378, 56, 7, 1, 1;

47232, 8460, 1020, 99, 9, 1, 1;

1694704, 252087, 26015, 2134, 154, 11, 1, 1;

73552752, 9392890, 855478, 61919, 3848, 221, 13, 1, 1; ...

in which row n equals row (n-1) of T^(2*n-1) followed by '1' for n > 0.

PROG

(PARI) {a(n) = my(A=[1]); for(i=1, n, A=concat(A, 0); m=#A; A[m] = Vec( (1+x +x*O(x^m))^(m^2)/Ser(A) )[m] ); A[n+1]}

for(n=0, 30, print1(a(n), ", "))

CROSSREFS

Cf. A132618, A304190, A304191, A304192, A132615.

Sequence in context: A156482 A173346 A319166 * A208661 A262123 A005749

Adjacent sequences:  A304190 A304191 A304192 * A304194 A304195 A304196

KEYWORD

nonn

AUTHOR

Paul D. Hanna, May 07 2018

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 27 17:58 EST 2020. Contains 331296 sequences. (Running on oeis4.)