If n is even then a(n) = n!/( 2^(n/2)*(n/2)! ), otherwise a(n) = n!/( 3*2^((n-1)/2)*((n-3)/2)! ).

A259877

If n is even then a(n) = n!/( 2^(n/2)*(n/2)! ), otherwise a(n) = n!/( 3*2^((n-1)/2)*((n-3)/2)! ).

Terms

    a(0) =1a(1) =1a(2) =3a(3) =10a(4) =15a(5) =105a(6) =105a(7) =1260a(8) =945a(9) =17325a(10) =10395a(11) =270270a(12) =135135a(13) =4729725a(14) =2027025a(15) =91891800a(16) =34459425a(17) =1964187225a(18) =654729075a(19) =45831035250a(20) =13749310575a(22) =316234143225

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