A203856 a(n) = (1/n) * Sum_{d|n} moebius(n/d) * Lucas(d)^5, where Lucas(n) = A000204(n).

1, 121, 341, 4141, 32210, 314717, 2930164, 28666025, 281724928, 2815289555, 28370872818, 288468152625, 2952876368200, 30409537607218, 314760765272250, 3272590619892675, 34158620991538050, 357779277130203136, 3758998894159780092, 39603542856374168550

Offset

1,2

Links

G. C. Greubel, Table of n, a(n) for n = 1..955

Formula

G.f.: 1/Product_{n>=1} (1 - Lucas(n)*x^n + (-1)^n*x^(2*n))^a(n) = exp(Sum_{n>=1} Lucas(n)^6 * x^n/n), which is the g.f. of A203806.

a(n) ~ phi^(5*n) / n, where phi = A001622 = (1+sqrt(5))/2 is the golden ratio. - Vaclav Kotesovec, Sep 02 2017

Example

G.f.: F(x) = 1/((1-x-x^2) * (1-3*x^2+x^4)^121 * (1-4*x^3-x^6)^341 * (1-7*x^4+x^8)^4141 * (1-11*x^5-x^10)^32210 * (1-18*x^6+x^12)^314717 * ... * (1 - Lucas(n)*x^n + (-1)^n*x^(2*n))^a(n) * ...)
where F(x) = exp( Sum_{n>=1} Lucas(n)^6 * x^n/n ) = g.f. of A203806:
F(x) = 1 + x + 365*x^2 + 1730*x^3 + 97390*x^4 + 948562*x^5 + ...
where
log(F(x)) = x + 3^6*x^2/2 + 4^6*x^3/3 + 7^6*x^4/4 + 11^6*x^5/5 + 18^6*x^6/6 + 29^6*x^7/7 + 47^6*x^8/8 + ... + Lucas(n)^6*x^n/n + ...

Mathematica

a[n_] := DivisorSum[n, MoebiusMu[n/#]*LucasL[#]^5&]/n; Array[a, 20] (* Jean-François Alcover, Dec 07 2015 *)

Prog

(PARI) {a(n)=if(n<1, 0, sumdiv(n, d, moebius(n/d)*(fibonacci(d-1)+fibonacci(d+1))^5)/n)}
(PARI) {Lucas(n)=fibonacci(n-1)+fibonacci(n+1)}
{a(n)=local(F=exp(sum(m=1, n, Lucas(m)^6*x^m/m)+x*O(x^n))); if(n==1, 1, polcoeff(F*prod(k=1, n-1, (1 - Lucas(k)*x^k + (-1)^k*x^(2*k) +x*O(x^n))^a(k)), n)/Lucas(n))}

Crossrefs

Cf. A203806, A203853, A203854, A203855, A203857, A203858, A203859, A203800.

Sequence in context: A254971 A112075 A068872 * A216166 A208242 A167721

Adjacent sequences: A203853 A203854 A203855 * A203857 A203858 A203859

Keyword

nonn

Author

Paul D. Hanna, Jan 07 2012

Status

approved