A089011 a(n) = 1 if n is an exponent of the Weyl group W(E_7), 0 otherwise.

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

Author

Paul Boddington, Nov 03 2003

Keywords

• easy
• nonn

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.

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000
• Index entries for characteristic functions

Crossrefs

Cf. A005763, A089010.

Programs

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 */

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)).