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A094876 a(1) = a(2) = a(3) = a(4) = a(5) = a(6) = 1; then a(n) = sum( a(2*i)*a(3*j)) where 1< = i< = n, 1< = j< = n and 2*i+3*j = n. 1

%I #12 Aug 23 2017 05:36:42

%S 1,1,1,1,1,1,1,1,1,1,2,1,2,2,2,2,5,2,5,5,5,5,14,5,14,14,14,14,42,14,

%T 42,42,42,42,132,42,132,132,132,132,429,132,429,429,429,429,1430,429,

%U 1430,1430,1430,1430,4862,1430,4862,4862,4862,4862,16796,4862,16796,16796

%N a(1) = a(2) = a(3) = a(4) = a(5) = a(6) = 1; then a(n) = sum( a(2*i)*a(3*j)) where 1< = i< = n, 1< = j< = n and 2*i+3*j = n.

%H Antti Karttunen, <a href="/A094876/b094876.txt">Table of n, a(n) for n = 1..1001</a>

%F (a(n)) satisfies : a(k)=1 for 1<=k<=8 then for n>=1 a(6n+2)=a(6n+3)=a(6n+4)=a(6n+6); a(6n+5)=a(6n+7)=a(6*n+2)+A000245(n)

%F a(6n-1) = a(6n+1) = a(6n+2) = a(6n+3) = a(6n+4) = a(6n+6) = A000108(n) except a(-1) = 0; generating function = (1-sqrt(1-4x^6))(1+x^2+x^3+x^4+x^5+x^7)/(2x^7)-1/x. - Alec Mihailovs (alec(AT)mihailovs.com), Jun 16 2004

%p A094876:=proc(N) local n; if N<1 then 0 else n:=floor((N-1)/6)+`if`(N mod 6=5,1,0); binomial(2*n,n)/(n+1) fi end; seq(A094876(N), N=1..62);

%t Rest[CoefficientList[Series[(1-Sqrt[1-4x^6])(1+x^2+x^3+x^4+x^5+x^7)/ (2x^7)- 1/x,{x,0,70}],x]] (* _Harvey P. Dale_, Aug 29 2011 *)

%o (PARI) v=vector(90,j,1);for(n=7,90,A=sum(i=1,n,sum(j=1,n,if(2*i+3*j-n,0,v[2*i]*v[3*j])));v[n]=A);a(n)=v[n];

%Y Cf. A000108.

%K nonn

%O 1,11

%A _Benoit Cloitre_, Jun 14 2004

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