OFFSET
1,5
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..1857
FORMULA
Given an integer t >= 1 and initial values u = [a_0, a_1, ..., a_{t-1}], we may define an infinite sequence Phi(u) by setting a_n = a_{n-1} + a_0*a_{n-1} + a_1*a_{n-2} + ... + a_{n-2}*a_1 for n >= t. For example, Phi([1]) is the Catalan numbers A000108. The present sequence is Phi([1,1,1,1]). - Gary W. Adamson, Oct 27 2008
Conjecture: n*a(n) +(n+1)*a(n-1) +10*(-2*n+5)*a(n-2) +2*(2*n-9)*a(n-3) +2*(14*n-79)*a(n-4) +40*(n-7)*a(n-5)=0. - R. J. Mathar, Jan 25 2015
G.f.: 1/2 - sqrt(8*x^4+4*x^3-4*x+1)/2. - Vaclav Kotesovec, Jan 25 2015
Recurrence: n*a(n) = 2*(2*n-3)*a(n-1) - 2*(2*n-9)*a(n-3) - 8*(n-6)*a(n-4). - Vaclav Kotesovec, Jan 25 2015
MAPLE
Phi:=proc(t, u, M) local i, a; a:=Array(0..M);
for i from 0 to t-1 do a[i]:=u[i+1]; od:
for i from t to M do a[i]:=a[i-1]+add(a[j]*a[i-1-j], j=0..i-2); od:
[seq(a[i], i=0..M)]; end;
Phi(4, [1, 1, 1, 1], 30);
# N. J. A. Sloane, Oct 29 2008
MATHEMATICA
nmax = 30; aa = ConstantArray[0, nmax]; aa[[1]] = 1; aa[[2]] = 1; aa[[3]] = 1; aa[[4]] = 1; Do[aa[[n]] = Sum[aa[[k]]*aa[[n-k]], {k, 1, n-1}], {n, 5, nmax}]; aa (* Vaclav Kotesovec, Jan 25 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved