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A255886
Number of orderings of the edges of the labeled complete graph K_n such that the graph induced by the first k edges is connected for every k=1,2,...,binomial(n,2).
1
1, 1, 6, 576, 2073600, 498161664000, 12385682950717440000, 45484508287062207627264000000, 33297304775599549535597153400913920000000, 6298496203530014357849150420174490961843322880000000000, 387030157006015555733158587399026951851936435957496524308480000000000000
OFFSET
1,3
FORMULA
For n>1, a(n) = binomial(n,2)! * 2^(n-2) / A000108(n-1).
MATHEMATICA
Join[{1}, Table[Binomial[n, 2]!*2^(n-2)*n/Binomial[2*n-2, n-1], {n, 2, 20}]] (* G. C. Greubel, Aug 03 2018 *)
PROG
(PARI) {a(n) = if( n<2, n>0, binomial(n, 2)! * 2^(n-2) * n / binomial(2*n-2, n-1))}; /* Michael Somos, Jul 23 2015 */
(Magma) [1] cat [Factorial(Binomial(n, 2))*2^(n-2)*n/Binomial(2*n-2, n-1): n in [2..20]]; // G. C. Greubel, Aug 03 2018
CROSSREFS
KEYWORD
nonn,nice
AUTHOR
Max Alekseyev, Mar 09 2015
STATUS
approved