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A237644 G.f. satisfies: a(n) = [x^n] ( A(x)^n + 1/A(x)^n ) for n>1, with a(0)=a(1)=1. 2
1, 1, 4, 63, 2116, 113550, 8687239, 891701755, 118110608484, 19625931563166, 4001492423904134, 983010151440620919, 286534726440573778723, 97810529840988133377195, 38660405402434292659485223, 17520204438205012495544783268 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Paul D. Hanna, Table of n, a(n) for n = 0..200

FORMULA

a(n) ~ c * 2^n * n^(2*n + 1) / exp(2*n), where c = 2.15155017267809206855547... - Vaclav Kotesovec, Aug 11 2021

EXAMPLE

G.f.: A(x) = 1 + x + 4*x^2 + 63*x^3 + 2116*x^4 + 113550*x^5 + 8687239*x^6 +...

Given the table of coefficients of x^k in A(x)^n, for {-oo < n < oo}:

...

[1,-7,  0,-301,-11634, -679252,-54467609,-5754393863, ...];

[1,-6, -3,-266,-10260, -593352,-47319971,-4982057256, ...];

[1,-5, -5,-230, -8800, -504011,-39971530,-4193722200, ...];

[1,-4, -6,-192, -7249, -411076,-32416322,-3389053044, ...];

[1,-3, -6,-151, -5601, -314385,-24648147,-2567705130, ...];

[1,-2, -5,-106, -3849, -213766,-16660556,-1729324458, ...];

[1,-1, -3, -56, -1985, -109036, -8446837, -873547334, ...];

[1, 0,  0,   0,     0,       0,        0,          0, ...];

[1, 1,  4,  63,  2116,  113550,  8687239,  891701755, ...];

[1, 2,  9, 134,  4374,  231836, 17622475, 1801953004, ...];

[1, 3, 15, 214,  6786,  355095, 26813632, 2731160112, ...];

[1, 4, 22, 304,  9365,  483580, 36268982, 3679741188, ...];

[1, 5, 30, 405, 12125,  617561, 45997165, 4648126560, ...];

[1, 6, 39, 518, 15081,  757326, 56007210, 5636759274, ...];

[1, 7, 49, 644, 18249,  903182, 66308557, 6646095618, ...];

...

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

[2, 0,  0,   0,    0,      0,        0,         0, ...];

[2, 0,  1,   7,  131,   4514,   240402,  18154421, ...];

[2, 0,  4,  28,  525,  18070,   961919,  72628546, ...];

[2, 0,  9,  63, 1185,  40710,  2165485, 163454982, ...];

[2, 0, 16, 112, 2116,  72504,  3852660, 290688144, ...];

[2, 0, 25, 175, 3325, 113550,  6025635, 454404360, ...];

[2, 0, 36, 252, 4821, 163974,  8687239, 654702018, ...];

[2, 0, 49, 343, 6615, 223930, 11840948, 891701755, ...];

...

such that the main diagonal yields this sequence for n>1.

PROG

(PARI) {a(n)=local(A=vector(n+1, i, 1)); for(n=2, #A-1, A[n+1] = Vec(Ser(A)^n + 1/Ser(A)^n)[n+1]); A[n+1]}

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

(PARI) /* Build vector of n=0..30 terms (faster): */

{A=vector(31, i, 1); for(n=2, #A-1, A[n+1] = Vec(Ser(A)^n + 1/Ser(A)^n)[n+1]); A}

CROSSREFS

Sequence in context: A349075 A299428 A274392 * A024256 A292394 A351779

Adjacent sequences:  A237641 A237642 A237643 * A237645 A237646 A237647

KEYWORD

nonn

AUTHOR

Paul D. Hanna, May 02 2014

STATUS

approved

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Last modified May 21 00:36 EDT 2022. Contains 353886 sequences. (Running on oeis4.)