E.g.f. 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 ).
RELATED SERIES.
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 ).
SPECIFIC VALUES.
At x = 1/2,
C(1/2) = 1.13133757946411922642102833324416139...
S(1/2) = 0.52907912329606456055608764850290077...
log(C(1/2) + S(1/2)) = 0.50706859662590456104854330721421537...
At x = 1,
C(1) = 1.61616724447561044622618032294959193...
S(1) = 1.26964426597212165112687564431552303...
log(C(1) + S(1)) = 1.05980614652360497313310791544203867...
At x = 2,
C(2) = 7.0181980831554020705059330009720760...
S(2) = 6.9465894030384550946994132182413166...
log(C(2) + S(2)) = 2.636538981679765615420983831302958...
At x = 3, the power series for C(x) and S(x) diverge.
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