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A089011
a(n) = 1 if n is an exponent of the Weyl group W(E_7), 0 otherwise.
4
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, 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, 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
OFFSET
1,1
COMMENTS
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.
FORMULA
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
G.f.: x*(1-x^12)*(1-x^14)/((1-x^4)*(1-x^6)).
PROG
(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 */
CROSSREFS
Sequence in context: A141728 A141737 A285301 * A267043 A266444 A267679
KEYWORD
easy,nonn
AUTHOR
Paul Boddington, Nov 03 2003
STATUS
approved