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A280790 E.g.f. A(x) satisfies: A( sin( A( sinh(x) ) ) ) = x. 7
1, 4, 2320, 9857600, 159122080000, 7098806416000000, 686863244097538560000, 143579312211740504320000000, 27634174819420517051458560000000, 103635121107833144489335056076800000000, -624322694794393812097710416148436992000000000, 9870191061692402402605200350045038131191808000000000, -258786046753018245774392957793266127246933652766720000000000, 11248188901093330352571154620038385487188031846809616384000000000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The series reversion of the e.g.f. is defined by A280792.

LINKS

Paul D. Hanna, Table of n, a(n) for n = 1..50

FORMULA

E.g.f. A(x) = Sum_{n>=1} a(n) * x^(4*n-3)/(4*n-3)! satisfies:

(1) A( sin( A( sinh(x) ) ) ) = x.

(2) A( sinh( A( sin(x) ) ) ) = x.

(3) sin( A( sinh( A(x) ) ) ) = x.

(4) sinh( A( sin( A(x) ) ) ) = x.

(5) A( sinh(A(x)) ) = asin(x).

(6) A( sin(A(x)) ) = asinh(x).

(7) Series_Reversion( A(x) ) = sin( A(sinh(x)) ) = sinh( A(sin(x)) ).

EXAMPLE

E.g.f.: A(x) = x + 4*x^5/5! + 2320*x^9/9! + 9857600*x^13/13! + 159122080000*x^17/17! + 7098806416000000*x^21/21! + 686863244097538560000*x^25/25! + 143579312211740504320000000*x^29/29! + 27634174819420517051458560000000*x^33/33! + 103635121107833144489335056076800000000*x^37/37! - 624322694794393812097710416148436992000000000*x^41/41! +...

such that A( sin( A( sinh(x) ) ) ) = x.

Note that A( A( sin( sinh(x) ) ) ) is NOT equal to x; the composition of these functions is not commutative.

The e.g.f. as a series with reduced fractional coefficients begins:

A(x) = x + 1/30*x^5 + 29/4536*x^9 + 6161/3891888*x^13 + 382505/855017856*x^17 + 50189525/361219896576*x^21 + 134894899309/3046287794457600*x^25 + 195216389950265/12021626449023916032*x^29 + ...

RELATED SERIES.

A( sinh(x) ) = x + x^3/3! + 5*x^5/5! + 141*x^7/7! + 6185*x^9/9! + 482681*x^11/11! + 55181165*x^13/13! + 8650849221*x^15/15! + 1806577140945*x^17/17! + 482615036315761*x^19/19! + 160833575943581525*x^21/21! + 65507016886932658301*x^23/23! + 32006289578900322278905*x^25/25! + ...

The series reversion of A( sinh(x) ) equals A( sin(x) ), which begins:

A( sin(x) ) = x - x^3/3! + 5*x^5/5! - 141*x^7/7! + 6185*x^9/9! - 482681*x^11/11! + 55181165*x^13/13! + ...

sinh( A(x) ) = x + x^3/3! + 5*x^5/5! + 85*x^7/7! + 2825*x^9/9! + 151625*x^11/11! + 12098125*x^13/13! + 1339476125*x^15/15! + 196410020625*x^17/17! + 37062144900625*x^19/19! + 8772471210303125*x^21/21! + 2519410212081953125*x^23/23! + 854580849916226265625*x^25/25! + ... + A318635(n)*x^(2*n-1)/(2*n-1)! + ...

The series reversion of sinh( A(x) ) equals sin( A(x) ), which begins:

sin( A(x) ) = x - x^3/3! + 5*x^5/5! - 85*x^7/7! + 2825*x^9/9! - 151625*x^11/11! + 12098125*x^13/13! + ...

The series reversion of A(x) = sin(A(sinh(x))) = sinh(A(sin(x))), and begins:

Series_Reversion( A(x) ) = x - 4*x^5/5! - 304*x^9/9! + 648896*x^13/13! + 2650020096*x^17/17! - 142483330376704*x^21/21! + 24311838501965418496*x^25/25! +...+ A280792(n)*x^(4*n-3)/(4*n-3)! + ...

PROG

(PARI) {a(n) = my(A=x +x*O(x^(4*n+1))); for(i=1, 2*n, A = A + (x - subst( sin(A) , x, sinh(A) ) )/2; H=A ); (4*n-3)!*polcoeff(A, 4*n-3)}

for(n=1, 20, print1(a(n), ", "))

CROSSREFS

Cf. A280791, A280792, A280793, A318635.

Sequence in context: A343695 A097476 A047676 * A079187 A131587 A066850

Adjacent sequences: A280787 A280788 A280789 * A280791 A280792 A280793

KEYWORD

sign

AUTHOR

Paul D. Hanna, Jan 08 2017

STATUS

approved

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Last modified February 6 11:11 EST 2023. Contains 360104 sequences. (Running on oeis4.)