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A337577 O.g.f. A(x) satisfies: [x^n] exp( n^2*(n-1) * x/A(x) ) = 0 for n > 0. 2
1, 2, 22, 1616, 286700, 90914400, 44673096808, 31286975152640, 29552473932597968, 36189841095064294016, 55768927589536556250016, 105641404186261853184309888, 241363180288689801902138103872, 654744988347389437898766097063424 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

It is remarkable that this sequence consists entirely of integers.

LINKS

Table of n, a(n) for n=0..13.

FORMULA

Given o.g.f. A(x), define B(x) = A(x*B(x)), then B(x) is the o.g.f. of A337578 and satisfies [x^n] exp( n*(n+1)^2*x ) / B(x)^(n+1) = 0 for n>0.

EXAMPLE

O.g.f.: A(x) = 1 + 2*x + 22*x^2 + 1616*x^3 + 286700*x^4 + 90914400*x^5 + 44673096808*x^6 + 31286975152640*x^7 + 29552473932597968*x^8 + ...

ILLUSTRATION OF DEFINITION.

The table of coefficients of x^k/k! in exp( n*(n-1)^2 * x/A(x) ) begins:

n=0: [1, 0, 0, 0, 0, 0, 0, ...];

n=1: [1, 0, 0, 0, 0, 0, 0, ...];

n=2: [1, 4, 0, -560, -154880, -137342976, -261610747904, ...];

n=3: [1, 18, 252, 0, -822960, -670328352, -1230620630976, ...];

n=4: [1, 48, 2112, 77760, 0, -2077949952, -3628874151936, ...];

n=5: [1, 100, 9600, 869200, 68473600, 0, -8724419840000, ...];

n=6: [1, 180, 31680, 5423760, 890714880, 130187520000, 0, ...];

n=7: [1, 294, 85260, 24343200, 6817260240, 1850897137824, 453595543361856, 0, ...]; ...

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

RELATED SERIES.

Define B(x) = A(x*B(x)), which begins

B(x) = 1 + 2*x + 26*x^2 + 1756*x^3 + 301140*x^4 + 94035272*x^5 + 45829458720*x^6 + 31938032357440*x^7 + ... + A337578(n)*x^n + ...

then the table of coefficients of x^k/k! in exp( n*(n+1)^2*x ) / B(x)^(n+1) begins:

n=0: [1, -2, -44, -9960, -7049664, -11131647360, -32715852151680, ...];

n=1: [1, 0, -96, -20480, -14247072, -22395261696, -65687348011520, ...];

n=2: [1, 12, 0, -34176, -22928112, -34905615552, -100977330265344, ...];

n=3: [1, 40, 1408, 0, -34275648, -51114811392, -142803802229760, ...];

n=4: [1, 90, 7860, 613000, 0, -71887626240, -199085724252800, ...];

n=5: [1, 168, 27936, 4535040, 663960096, 0, -269327647065600, ...];

n=6: [1, 280, 78064, 21598080, 5858601168, 1443397611264, 0, ...];

n=7: [1, 432, 186240, 80041984, 34200321408, 14371727121408, 5514496883009536, 0, ...]; ...

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

Also note that B(x) = (1/x)*Series_Reversion( x/A(x) ) and A(x) = B(x/A(x)).

PROG

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

for(n=0, 20, print1(a(n), ", "))

CROSSREFS

Cf. A337578, A337575, A337457.

Sequence in context: A202947 A177410 A193486 * A054948 A330124 A104149

Adjacent sequences:  A337574 A337575 A337576 * A337578 A337579 A337580

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Sep 02 2020

STATUS

approved

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Last modified May 13 02:02 EDT 2021. Contains 343836 sequences. (Running on oeis4.)