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A325292 E.g.f. S(x), where C(x*y) + S(x*y) = exp( Integral Integral C(x*y) dx dy ) such that C(x)^2 - S(x)^2 = 1. 4
1, 8, 576, 160768, 123535360, 212713734144, 716196297048064, 4280584942657732608, 42250703121584165486592, 651154631135458759089848320, 14983590319172065236171175755776, 496301942561421311900528265903734784, 22953613919171561374366988621726483480576, 1444609513446024762131466039751756562435145728 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Unsigned version of A326552.

LINKS

Paul D. Hanna, Table of n, a(n) for n = 0..99

FORMULA

E.g.f. S(x) = Sum_{n>=0} a(n)*x^(2*n+1)/(2*n+1)!^2, where series S(x) and related series C(x) satisfy the following relations.

(1.a) C(x)^2 - S(x)^2 = 1.

(1.b) C'(x)/S(x) = S'(x)/C(x) =  1/x * Integral C(x) dx.

(2.a) S(x) = Integral C(x)/x * (Integral C(x) dx) dx.

(2.b) C(x) = 1 + Integral S(x)/x * (Integral C(x) dx) dx.

(3.a) C(x) + S(x) = exp( Integral 1/x * (Integral C(x) dx) dx ).

(3.b) C(x) = cosh( Integral 1/x * (Integral C(x) dx) dx ).

(3.c) S(x) = sinh( Integral 1/x * (Integral C(x) dx) dx ).

Integration.

(4.a) S(x*y) = Integral C(x*y) * (Integral C(x*y) dy) dx.

(4.b) C(x*y) = 1 + Integral S(x*y) * (Integral C(x*y) dy) dx.

(4.c) S(x*y) = Integral C(x*y) * (Integral C(x*y) dx) dy.

(4.d) C(x*y) = 1 + Integral S(x*y) * (Integral C(x*y) dx) dy.

Exponential.

(5.a) C(x*y) + S(x*y) = exp( Integral Integral C(x*y) dx dy ).

(5.b) C(x*y) = cosh( Integral Integral C(x*y) dx dy ).

(5.c) S(x*y) = sinh( Integral Integral C(x*y) dx dy ).

Derivatives.

(6.a) d/dx S(x*y) = C(x*y) * Integral C(x*y) dy.

(6.b) d/dx C(x*y) = S(x*y) * Integral C(x*y) dy.

(6.c) d/dy S(x*y) = C(x*y) * Integral C(x*y) dx.

(6.d) d/dy C(x*y) = S(x*y) * Integral C(x*y) dx.

EXAMPLE

E.g.f. S(x) = x + 8*x^3/3!^2 + 576*x^5/5!^2 + 160768*x^7/7!^2 + 123535360*x^9/9!^2 + 212713734144*x^11/11!^2 + 716196297048064*x^13/13!^2 + 4280584942657732608*x^15/15!^2 + 42250703121584165486592*x^17/17!^2 + 651154631135458759089848320*x^19/19!^2 + 14983590319172065236171175755776*x^21/21!^2 + ...

where S(x) = sinh( Integral 1/x * (Integral C(x) dx) dx ),

also, S(x*y) = sinh( Integral Integral C(x*y) dx dy ).

RELATED SERIES.

C(x) = 1 + 2*x^2/2!^2 + 56*x^4/4!^2 + 8336*x^6/6!^2 + 3985792*x^8/8!^2 + 4679517952*x^10/10!^2 + 11427218287616*x^12/12!^2 + 51793067942397952*x^14/14!^2 + 400951893341645930496*x^16/16!^2 + 4975999084909976839454720*x^18/18!^2 + 94178912073481319162642169856*x^20/20!^2 + ...

where C(x) = cosh( Integral 1/x * (Integral C(x) dx) dx ),

also, C(x*y) = cosh( Integral Integral C(x*y) dx dy ).

PROG

(PARI) {a(n) = my(C=1, S=x); for(i=1, 2*n+1,

S = intformal( C/x * intformal( C +x*O(x^(2*n+1)) ) );

C = 1 + intformal( S/x * intformal( C +x*O(x^(2*n+1)) ) ); ); (2*n+1)!^2*polcoeff(S, 2*n+1)}

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

CROSSREFS

Cf. A325290 (C+S), A325291 (C).

Cf. A326552.

Sequence in context: A058045 A086641 A248706 * A326552 A303933 A188780

Adjacent sequences:  A325289 A325290 A325291 * A325293 A325294 A325295

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Apr 16 2019

STATUS

approved

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Last modified December 5 20:39 EST 2021. Contains 349558 sequences. (Running on oeis4.)