|
%I #15 Dec 26 2018 16:53:42
%S 1,0,0,0,1,0,1,0,1,0,1,0,1,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%T 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%U 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
%N a(n) = 1 if n is an exponent of the Weyl group W(E_7), 0 otherwise.
%C The exponents are 1, 5, 7, 9, 11, 13, 17. The point of this sequence is that a similar generating function gives the exponents for any finite Coxeter group.
%H Antti Karttunen, <a href="/A089011/b089011.txt">Table of n, a(n) for n = 1..10000</a>
%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>
%F Euler transform of length 14 sequence [ 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, -1, 0, -1]. - _Michael Somos_, Mar 07 2007
%F G.f.: x*(1-x^12)*(1-x^14)/((1-x^4)*(1-x^6)).
%o (PARI) {a(n)=if(n<1, 0, polcoeff( x^17+x^13+x^11+x^9+x^7+x^5+x, n))} /* _Michael Somos_, Mar 07 2007 */
%Y Cf. A005763, A089010.
%K easy,nonn
%O 1,1
%A _Paul Boddington_, Nov 03 2003
|
