%I #20 Feb 23 2018 10:48:17

%S 1,4,31,486,15381,978768,124918731,31932406170,16337382642945,

%T 16723323142761060,34243057328337866295,140246638967945496322350,

%U 1148847521944847479468879725,18822284044001939139425413111800,616761496621711735518439444437389475

%N (n-1)-st elementary symmetric function of {1,3,7,15,31,63,...-1+2^n}.

%H Clark Kimberling, <a href="/A203011/b203011.txt">Table of n, a(n) for n = 1..50</a>

%F a(n) = c * 2^(n*(n+1)/2), where c = A048651 * A065442 = 0.4639944324508904477884... . - _Vaclav Kotesovec_, Oct 10 2016

%p SymmPolyn := proc(L::list,n::integer)

%p local c,a,sel;

%p a :=0 ;

%p sel := combinat[choose](nops(L),n) ;

%p for c in sel do

%p a := a+mul(L[e],e=c) ;

%p end do:

%p a;

%p end proc:

%p A203011 := proc(n)

%p local L,k ;

%p L := [seq(2^k-1,k=1..n)] ;

%p SymmPolyn(L,n-1) ;

%p end proc: # _R. J. Mathar_, Sep 23 2016

%t f[k_] := -1 + 2^k; t[n_] := Table[f[k], {k, 1, n}]

%t a[n_] := SymmetricPolynomial[n - 1, t[n]]

%t Table[a[n], {n, 1, 16}] (* A203011 *)

%t Table[Product[2^k-1,{k,1,n}] * Sum[1/(2^k-1),{k,1,n}],{n,1,16}] (* _Vaclav Kotesovec_, Sep 06 2014 *)

%Y Cf. A122743.

%K nonn

%O 1,2

%A _Clark Kimberling_, Dec 29 2011