

A008614


Molien series of 3dimensional representation of group GL(3,2) (= L(2,7)); a simple group of order 168.


3



1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 0, 2, 0, 2, 0, 3, 0, 3, 1, 3, 0, 4, 1, 4, 1, 5, 1, 5, 1, 6, 2, 6, 2, 7, 2, 7, 3, 8, 3, 9, 3, 9, 4, 10, 4, 11, 5, 11, 5, 12, 6, 13, 6, 14, 7, 14, 7, 16, 8, 16, 9, 17, 9, 18, 10, 19, 11, 20, 11, 21, 12, 22, 13, 23, 14, 24, 14, 25, 16, 26, 16, 28, 17, 28, 18, 30
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OFFSET

0,13


COMMENTS

The simple group of order 168 expressed as a group of linear substitutions on three variables has invariants of degrees 4, 6, 14 which are rationally independent. The invariant of degree 4 is x1*x2^3 + x2*x3^3 + x3*x1^3 (Klein's quartic curve).  Michael Somos, Mar 18 2015


REFERENCES

D. J. Benson, Polynomial Invariants of Finite Groups, Cambridge, 1993, p. 101.
W. Burnside, Theory of Groups of Finite Order, Dover Publications, NY, 1955, section 267, page 363. There is a typo in his formula: the term with numerator 21 should have denominator (1+x)(1x^2). [Added by N. J. A. Sloane, Mar 01 2012]
T. A. Springer, Invariant Theory, Lecture Notes in Math., Vol. 585, Springer, p. 97.


LINKS

T. D. Noe, Table of n, a(n) for n = 0..1000
Index entries for Molien series
Index entries for linear recurrences with constant coefficients, signature (1,0,1,2,1,0,0,0,0,1,2,1,0,1,1).


FORMULA

Euler transform of length 42 sequence [0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1].  Michael Somos, Oct 11 2006
G.f.: (1  x^42) / ((1  x^4) * (1  x^6) * (1  x^14) * (1  x^21)).  Michael Somos, Oct 11 2006
a(n) = a(3  n). a(n) = a(n4) + a(n6)  a(n10) + a(n14)  a(n18)  a(n20) + a(n24) for all n in Z.  Michael Somos, Oct 11 2006
a(2*n + 21) = a(2*n) = A008671(n) for all n in Z.
a(n) ~ 1/336*n^2.  Ralf Stephan, Apr 29 2014
a(n)= a(n1) +a(n3) +2*a(n4) +a(n5) a(n10) 2*a(n11) a(n12) +a(n14) +a(n15).  R. J. Mathar, Dec 18 2014
G.f.: (1/168) * ( 1 / (1  x)^3 + 21 / ((1 + x) * (1  x^2)) + 56 / (1  x^3) + 42 / ((1  x) * (1 + x^2)) + 24 * (1  x) * (2 + 3*x + 2*x^2) / (1 + x + x^2 + x^3 + x^4 + x^5 + x^6)). [Burnside]  Michael Somos, Mar 18 2015


EXAMPLE

G.f. = 1 + x^4 + x^6 + x^8 + x^10 + 2*x^12 + 2*x^14 + 2*x^16 + 3*x^18 + ...


MAPLE

(1+x^21)/(1x^4)/(1x^6)/(1x^14);


MATHEMATICA

LinearRecurrence[{1, 0, 1, 2, 1, 0, 0, 0, 0, 1, 2, 1, 0, 1, 1}, {1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 0, 2}, 100] (* Harvey P. Dale, Jan 17 2015 *)
a[ n_] := Module[{m = If[ n < 0, 3  n, n]}, m = If[ OddQ[m], m  21, m] / 2; SeriesCoefficient[ 1 / ((1  x^2) (1  x^3) (1  x^7)), {x, 0, m}]]; (* Michael Somos, Mar 18 2015 *)


PROG

(PARI) {a(n) = if( n%2, n=21); n/=2; if( n<11, n=12n); polcoeff( 1 / ((1x^2) * (1x^3) * (1x^7)) + x * O(x^n), n)}; /* Michael Somos, Oct 11 2006 */


CROSSREFS

Cf. A008671.
Sequence in context: A281009 A284443 A260160 * A036663 A209457 A096577
Adjacent sequences: A008611 A008612 A008613 * A008615 A008616 A008617


KEYWORD

nonn,easy,nice


AUTHOR

N. J. A. Sloane.


STATUS

approved



