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A280627 E.g.f. D(x) satisfies: C(x)^2 - S(x)^2 = 1 and D(x)^4 - S(x)^4 = 1, where functions S(x) and C(x) are described by A280625 and A280626, respectively. 5

%I

%S 1,0,6,120,4284,382560,40975176,6524350560,1420005102864,

%T 386400824613120,133774424157792096,56530740636066364800,

%U 28642309445854790698944,17209537237868777504801280,12062425479867549597010598016,9764667204009505877211747479040,9042097280460821686724885486625024,9493787529624453974176836837131427840,11221110790852570214718646510965006951936,14830442526518302962134606954574648582420480

%N E.g.f. D(x) satisfies: C(x)^2 - S(x)^2 = 1 and D(x)^4 - S(x)^4 = 1, where functions S(x) and C(x) are described by A280625 and A280626, respectively.

%H Paul D. Hanna, <a href="/A280627/b280627.txt">Table of n, a(n) for n = 0..200</a>

%F E.g.f. D(x) = Sum_{n>=0} a(n)*x^(2*n)/(2*n)!, where related functions S = S(x), C = C(x), and D = D(x) possess the following properties.

%F (1.a) C^2 - S^2 = 1.

%F (1.b) D^4 - S^4 = 1.

%F Integrals.

%F (2.a) S = Integral C*D^3 dx.

%F (2.b) C = 1 + Integral S*D^3 dx.

%F (2.c) D = 1 + Integral C*S^3 dx.

%F (2.d) C + S = 1 + Integral D^3 * (C + S) dx.

%F (2.e) D^2 + S^2 = 1 + Integral 2*S*C*D * (D^2 + S^2) dx.

%F (2.f) D - S = 1 - Integral C * (D^3 - S^3) dx.

%F Exponential.

%F (3.a) C + S = exp( Integral D^3 dx ).

%F (3.b) D^2 + S^2 = exp( Integral 2*S*C*D dx ).

%F (3.d) C = cosh( Integral D^3 dx ).

%F (3.e) S = sinh( Integral D^3 dx ).

%F (3.f) D^2 = cosh( Integral 2*S*C*D dx ).

%F (3.g) S^2 = sinh( Integral 2*S*C*D dx ).

%F (3.h) sinh( Integral D^3 dx )^2 = sinh( Integral 2*S*C*D dx ).

%F Derivatives.

%F (4.a) S' = C*D^3.

%F (4.b) C' = S*D^3.

%F (4.c) D' = C*S^3.

%F (4.d) S'*D - D'*S = C.

%F (4.e) S'*C - C'*S = D^3.

%F (4.f) (C' + S')/(C + S) = D^3.

%F (4.g) (D^2 + S^2)'/(D^2 + S^2) = 2*S*C*D.

%F (4.h) (D' - S')/(D - S) = -C * (D^2 + D*S + S^2).

%e E.g.f.: D(x) = 1 + 6*x^4/4! + 120*x^6/6! + 4284*x^8/8! + 382560*x^10/10! + 40975176*x^12/12! + 6524350560*x^14/14! + 1420005102864*x^16/16! + 386400824613120*x^18/18! + 133774424157792096*x^20/20! + 56530740636066364800*x^22/22! + 28642309445854790698944*x^24/24! + 17209537237868777504801280*x^26/26! + 12062425479867549597010598016*x^28/28! +...

%e such that

%e (1) C(x)^2 - S(x)^2 = 1,

%e (2) D(x)^4 - S(x)^4 = 1,

%e where functions S(x) and C(x) are illustrated below.

%e RELATED SERIES.

%e S(x) = x + x^3/3! + 19*x^5/5! + 739*x^7/7! + 35641*x^9/9! + 3753721*x^11/11! + 500577499*x^13/13! + 91718242219*x^15/15! + 22737318482161*x^17/17! + 6983681901945841*x^19/19! + 2676021948941279779*x^21/21! + 1243547540389481251699*x^23/23! + 686920343453752746986281*x^25/25! + 446624144083900575607651561*x^27/27! +...

%e C(x) = 1 + x^2/2! + x^4/4! + 109*x^6/6! + 3889*x^8/8! + 292681*x^10/10! + 37275121*x^12/12! + 5709311029*x^14/14! + 1254902705569*x^16/16! + 350061261777361*x^18/18! + 120872805166945441*x^20/20! + 51564789352080559549*x^22/22! + 26284030671328082426449*x^24/24! + 15848108292907342195314841*x^26/26! + 11161807217694742818283238161*x^28/28! +...

%e C(x) + S(x) = 1 + x + x^2/2! + x^3/3! + x^4/4! + 19*x^5/5! + 109*x^6/6! + 739*x^7/7! + 3889*x^8/8! + 35641*x^9/9! + 292681*x^10/10! + 3753721*x^11/11! + 37275121*x^12/12! + 500577499*x^13/13! + 5709311029*x^14/14! + 91718242219*x^15/15! + 1254902705569*x^16/16! + 22737318482161*x^17/17! + 350061261777361*x^18/18! + 6983681901945841*x^19/19! + 120872805166945441*x^20/20! +...

%e such that C(x) + S(x) = exp( Integral D(x)^3 dx ).

%e C(x)^2 = 1 + 2*x^2/2! + 8*x^4/4! + 248*x^6/6! + 13952*x^8/8! + 981152*x^10/10! + 128012288*x^12/12! + 21334590848*x^14/14! + 4721317609472*x^16/16! + 1369528258007552*x^18/18! + 487519312215277568*x^20/20! + 212815485425900238848*x^22/22! + 111362541450468672929792*x^24/24! + 68655437948261593572810752*x^26/26! +...

%e such that C(x)^2 = 1 + S(x)^2.

%e D(x)^2 = 1 + 12*x^4/4! + 240*x^6/6! + 11088*x^8/8! + 1067520*x^10/10! + 120702912*x^12/12! + 20731576320*x^14/14! + 4706356447488*x^16/16! + 1338363800125440*x^18/18! + 482064458680691712*x^20/20! + 210556245001175040000*x^22/22! + 110103167770187282239488*x^24/24! + 68059391373987458643394560*x^26/26! +...

%e D(x)^3 = 1 + 18*x^4/4! + 360*x^6/6! + 20412*x^8/8! + 2054880*x^10/10! + 246667608*x^12/12! + 45345998880*x^14/14! + 10711766694672*x^16/16! + 3182147454332160*x^18/18! + 1190153458696009248*x^20/20! + 536990828063228035200*x^22/22! + 289633988053086885277632*x^24/24! + 184083367623416380788963840*x^26/26! +...

%e D(x)^4 = 1 + 24*x^4/4! + 480*x^6/6! + 32256*x^8/8! + 3344640*x^10/10! + 426353664*x^12/12! + 83091939840*x^14/14! + 20370678153216*x^16/16! + 6310701707796480*x^18/18! + 2444823498480943104*x^20/20! + 1138286636773997568000*x^22/22! + 632578480424353976549376*x^24/24! + 413014933705057627523973120*x^26/26! +...

%e such that D(x)^4 = 1 + S(x)^4.

%e D(x)^2 + S(x)^2 = 1 + 2*x^2/2! + 20*x^4/4! + 488*x^6/6! + 25040*x^8/8! + 2048672*x^10/10! + 248715200*x^12/12! + 42066167168*x^14/14! + 9427674056960*x^16/16! + 2707892058132992*x^18/18! + 969583770895969280*x^20/20! + 423371730427075278848*x^22/22! + 221465709220655955169280*x^24/24! + 136714829322249052216205312*x^26/26! +...

%e sqrt(D(x)^2 + S(x)^2) = 1 + x^2/2! + 7*x^4/4! + 139*x^6/6! + 6913*x^8/8! + 508921*x^10/10! + 57888967*x^12/12! + 9313574419*x^14/14! + 1984690709953*x^16/16! + 547467006437041*x^18/18! + 188946742298214727*x^20/20! + 79783392959511537499*x^22/22! + 40498043815904027702593*x^24/24! + 24314800861291379306213161*x^26/26! +...

%e such that sqrt(D(x)^2 + S(x)^2) = exp( Integral S(x)*C(x)*D(x) dx ).

%o (PARI) {a(n) = my(S=x, C=1, D=1); for(i=0, 2*n, S = intformal( C*D^3 + x*O(x^(2*n))); C = 1 + intformal( S*D^3 ); D = 1 + intformal( C*S^3 )); (2*n)!*polcoeff(D, 2*n)}

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

%Y Cf. A280625 (S), A280626 (C), A280628 (C+S), A280629 (sqrt(D^2+S^2)).

%K nonn

%O 0,3

%A _Paul D. Hanna_, Jan 06 2017

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Last modified January 18 19:19 EST 2020. Contains 331029 sequences. (Running on oeis4.)