A244430 E.g.f.: exp( Sum_{n>=1} Fibonacci(n)*x^n/n ).

1, 1, 2, 8, 44, 316, 2776, 28912, 347888, 4750064, 72548576, 1225540096, 22686824512, 456700011328, 9932944782464, 232113573798656, 5799735585095936, 154302762658308352, 4354977806995644928, 129961223706359609344, 4088626884119702752256, 135246429574930409348096

Offset

0,3

Links

Vaclav Kotesovec, Table of n, a(n) for n = 0..410

Tomislav Doslic and R. Sharafdini, Hosoya Index of Splices, Bridges, and Necklaces, in Distance, Symmetry, and Topology in Carbon Nanomaterials, 2016, pp 147-156. Part of the Carbon Materials: Chemistry and Physics book series (CMCP, volume 9), doi:10.1007/978-3-319-31584-3_10. See page 9, at the end of section 2, where a sequence with this recurrence although with different initial conditions is mentioned.

Formula

E.g.f.: ( (1 + x/Phi) / (1 - Phi*x) )^(sqrt(5)/5) where Phi = (sqrt(5)+1)/2.

E.g.f.: exp( Integral 1/(1-x-x^2) dx ).

a(n) ~ n! * 5^(1/(2*sqrt(5))) * n^(1/sqrt(5)-1) * ((1+sqrt(5))/2)^(n-1/sqrt(5)) / GAMMA(1/sqrt(5)). - Vaclav Kotesovec, Jun 28 2014

a(n) = n*a(n-1) + (n-1)*(n-2)*a(n-2) for a(0)=a(1)=1. - G. C. Greubel, May 02 2015

E.g.f.: sqrt(5)*Phi^(-2/sqrt(5))*( B((Phi + x)/sqrt(5); 2/(sqrt(5) Phi), (2 Phi)/sqrt(5)) - B(Phi/sqrt(5); 2/(sqrt(5) Phi), (2 Phi)/sqrt(5)) ), where B(z; a, b) is the Incomplete Beta function and a(0)=0, a(1)=a(2)=1. - G. C. Greubel, May 02 2015

0 = a(n)*(-72*a(n+2) +384*a(n+3) +772*a(n+4) -12*a(n+5) -64*a(n+6) +5*a(n+7)) +a(n+1)*(-124*a(n+3) -234*a(n+4) +74*a(n+5)) +a(n+2)*(+12*a(n+2) -54*a(n+3) -20*a(n+4) -30*a(n+5)) +a(n+3)*(+10*a(n+3) +25*a(n+4)) for all n>=0. - Michael Somos, Sep 24 2022

E.g.f.: exp((2/sqrt(5)) * arctanh(x*sqrt(5)/(2-x))). - Fabian Pereyra, Oct 11 2023

a(n) = n!*Sum_{k=0..n} binomial(n-1,k-1)*binomial(1/sqrt(5),k)*((1+sqrt(5))/2)^(n-k)*(sqrt(5))^k. - Fabian Pereyra, Oct 19 2023

Example

E.g.f.: A(x) = 1 + x + 2*x^2/2! + 8*x^3/3! + 44*x^4/4! + 316*x^5/5! + 2776*x^6/6! +...
where
log(A(x)) = x + x^2/2 + 2*x^3/3 + 3*x^4/4 + 5*x^5/5 + 8*x^6/6 + 13*x^7/7 + 21*x^8/8 + 34*x^9/9 +...+ A000045(n)*x^n/n +...

Maple

f:= gfun:-rectoproc({a(n) = n*a(n-1) + (n-1)*(n-2)*a(n-2), a(0)=1, a(1)=1}, a(n), remember):
seq(f(n), n=0..50); # Robert Israel, May 22 2015

Mathematica

a[ n_ ] := a[n] =(n-1)*(n-2)a[n-2]+n*a[n-1]; a[0] := 1; a[1] := 1 (* G. C. Greubel, May 02 2015 *)
RecurrenceTable[{a[0]==1, a[1]==1, a[n]==(n-1)*(n-2)a[n-2]+n*a[n-1]}, a, {n, 20}] (* G. C. Greubel, May 02 2015 *)

Prog

(PARI) {a(n)=n!*polcoeff(exp(intformal(1/(1-x-x^2 +x*O(x^n)))), n)}
for(n=0, 30, print1(a(n), ", "))
(Magma) [n le 2 select 1 else (n-1)*Self(n-1)+(n^2-5*n+6)*Self(n-2): n in [1..30]]; // Vincenzo Librandi, May 03 2015

Crossrefs

Cf. A244451, A244432, A000045.

Sequence in context: A216234 A123307 A293905 * A190818 A372156 A330444

Adjacent sequences: A244427 A244428 A244429 * A244431 A244432 A244433

Keyword

nonn

Author

Paul D. Hanna, Jun 27 2014

Status

approved