Search: id:A123618
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%I A123618
%S A123618 1,4,39,392,4420,52272,644231,8179600,106376580,1410528080,19006875580,
%T A123618 259613952864,3587352778256,50068405195200,704925148185495,
%U A123618 10001318622631200,142866058397606500,2053248549639210000
%N A123618 a(n) = A123610(2*n+2,n).
%C A123618 Related sequences: A123610(2n,n) = A123617(n); A123610(2n+1,n) = A000891(n); 
               A123610(2n+2,n)/(n+1) = A123619(n). a(n) is divisible by (n+1): a(n)/
               (n+1) = A123619(n).
%o A123618 (PARI) {a(n)=if(n==0,1,(1/(2*n+2))*sumdiv(2*n+2,d,if(gcd(n,d)==d, eulerphi(d)*binomial((2*n+2)/
               d,n/d)^2,0)))}
%Y A123618 Cf. A123610 (triangle); A123617, A000891, A123619.
%Y A123618 Sequence in context: A059945 A093851 A063035 this_sequence A046449 A068187 
               A024055
%Y A123618 Adjacent sequences: A123615 A123616 A123617 this_sequence A123619 A123620 
               A123621
%K A123618 nonn
%O A123618 0,2
%A A123618 Paul D. Hanna (pauldhanna(AT)juno.com), Oct 03 2006

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