login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A108995 a(n) = A108994(n)*2/(n+2) for n>=0. 6

%I #4 Mar 30 2012 18:36:46

%S 1,2,9,72,890,15456,352807,10093728,349534881,14270091790,

%T 672991000968,36076060520556,2169580363847949,144810568283675126,

%U 10631141835083823945,851921010801706760672,74031550751810889131475

%N a(n) = A108994(n)*2/(n+2) for n>=0.

%C a(n) is divisible by (n+1). A108994 is the third diagonal of triangle A108990, in which the g.f. of row n, R_n(x), satisfies: [x^k] R_{n+1}(x) = [x^k] (1 + x*R_n(x))^(n+1) for k=0..n+1.

%F a(n) = A108990(n+2, n)*2/(n+2) for n>=0.

%o (PARI) {a(n)=local(F=1);for(m=1,n+2,F=(1+x*F+x*O(x^n))^m);polcoeff(F,n)*2/(n+2)}

%Y Cf. A108990, A108991, A108992, A108993, A108994, A108996.

%K nonn

%O 0,2

%A _Paul D. Hanna_, Jun 15 2005

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 13:42 EDT 2024. Contains 371254 sequences. (Running on oeis4.)