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 A092351 Molien series for certain 16-dimensional group of order 322560 arising from genus-2 weight enumerators of singly-even (but not necessarily self-dual or self-orthogonal) binary codes. 1
 1, 1, 2, 3, 6, 9, 17, 27, 49, 79, 138, 225, 388, 634, 1069, 1750, 2904, 4706, 7677, 12302, 19715, 31137, 48994, 76133, 117637, 179718, 272692, 409558, 610615, 901812, 1322019, 1921168, 2771490, 3965936, 5635172, 7947036, 11132032, 15484913, 21402697, 29390457 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Robert Israel, Table of n, a(n) for n = 0..10000 G. Nebe, E. M. Rains and N. J. A. Sloane, Self-Dual Codes and Invariant Theory, Springer, Berlin, 2006. Index entries for linear recurrences with constant coefficients, signature (2, 1, -2, -2, 0, 2, -1, 3, -1, 0, 0, 3, -4, -5, 4, -4, 1, 2, 11, -5, 1, -2, -5, -1, -2, 0, -8, 19, 2, 2, -6, 3, -10, -7, 6, -11, 10, 6, 13, -10, 12, -6, -19, -4, 3, 7, -7, 20, -7, 7, 3, -4, -19, -6, 12, -10, 13, 6, 10, -11, 6, -7, -10, 3, -6, 2, 2, 19, -8, 0, -2, -1, -5, -2, 1, -5, 11, 2, 1, -4, 4, -5, -4, 3, 0, 0, -1, 3, -1, 2, 0, -2, -2, 1, 2, -1). FORMULA G.f. = f(x)/g(x) where f(x) = x^80 - x^79 - x^78 + 2*x^76 + x^74 + x^73 + 2*x^72 + 5*x^70 + 3*x^69 + 13*x^68 + 10*x^67 + 29*x^66 + 31*x^65 + 66*x^64 + 61*x^63 + 121*x^62 + 138*x^61 + 232*x^60 + 258*x^59 + 396*x^58 + 456*x^57 + 654*x^56 + 739*x^55 + 974*x^54 + 1098*x^53 + 1400*x^52 + 1529*x^51 + 1859*x^50 + 2013*x^49 + 2363*x^48 + 2486*x^47 + 2831*x^46 + 2923*x^45 + 3222*x^44 + 3233*x^43 + 3461*x^42 + 3406*x^41 + 3570*x^40 + 3406*x^39 + 3461*x^38 + 3233*x^37 + 3222*x^36 + 2923*x^35 + 2831*x^34 + 2486*x^33 + 2363*x^32 + 2013*x^31 + 1859*x^30 + 1529*x^29 + 1400*x^28 + 1098*x^27 + 974*x^26 + 739*x^25 + 654*x^24 + 456*x^23 + 396*x^22 + 258*x^21 + 232*x^20 + 138*x^19 + 121*x^18 + 61*x^17 + 66*x^16 + 31*x^15 + 29*x^14 + 10*x^13 + 13*x^12 + 3*x^11 + 5*x^10 + 2*x^8 + x^7 + x^6 + 2*x^4 - x^2 - x + 1 and g(x) = x^96 - 2*x^95 - x^94 + 2*x^93 + 2*x^92 - 2*x^90 + x^89 - 3*x^88 + x^87 - 3*x^84 + 4*x^83 + 5*x^82 - 4*x^81 + 4*x^80 - x^79 - 2*x^78 - 11*x^77 + 5*x^76 - x^75 + 2*x^74 + 5*x^73 + x^72 + 2*x^71 + 8*x^69 - 19*x^68 - 2*x^67 - 2*x^66 + 6*x^65 - 3*x^64 + 10*x^63 + 7*x^62 - 6*x^61 + 11*x^60 - 10*x^59 - 6*x^58 - 13*x^57 + 10*x^56 - 12*x^55 + 6*x^54 + 19*x^53 + 4*x^52 - 3*x^51 - 7*x^50 + 7*x^49 - 20*x^48 + 7*x^47 - 7*x^46 - 3*x^45 + 4*x^44 + 19*x^43 + 6*x^42 - 12*x^41 + 10*x^40 - 13*x^39 - 6*x^38 - 10*x^37 + 11*x^36 - 6*x^35 + 7*x^34 + 10*x^33 - 3*x^32 + 6*x^31 - 2*x^30 - 2*x^29 - 19*x^28 + 8*x^27 + 2*x^25 + x^24 + 5*x^23 + 2*x^22 - x^21 + 5*x^20 - 11*x^19 - 2*x^18 - x^17 + 4*x^16 - 4*x^15 + 5*x^14 + 4*x^13 - 3*x^12 + x^9 - 3*x^8 + x^7 - 2*x^6 + 2*x^4 + 2*x^3 - x^2 - 2*x + 1. PROG (MAGMA) K:=Rationals(); M:=MatrixAlgebra(K, 4); q1:=DiagonalMatrix(M, [1, -1, 1, -1]); p1:=DiagonalMatrix(M, [1, 1, -1, -1]); q2:=DiagonalMatrix(M, [1, 1, 1, -1]); h:=M![1, 1, 1, 1, 1, 1, -1, -1, 1, -1, 1, -1, 1, -1, -1, 1]/2; H:=MatrixGroup<4, K|q1, q2, h, p1>; permstomats:=function(L); n:=#L[1]; M:=MatrixAlgebra(Rationals(), n); a:=#L; MM:=[]; for i in [1..a] do Append(~MM, M ! 0); end for; for i in [1..a] do for j in [1..n] do MM[i][j][L[i][j]]:=1; end for; end for; return MM; end function; MM:=MatrixAlgebra(K, 16); hh:=TensorProduct(M ! 1, h); qq1:=TensorProduct(M ! 1, q1); pp1:=TensorProduct(M ! 1, p1); qq2:=TensorProduct(M ! 1, q2); perm:=sub; Order(perm); pp:=Setseq(Generators(perm)); L:=[Eltseq(pp[1]), Eltseq(pp[2]), Eltseq(pp[3]), Eltseq(pp[4])]; ML:=permstomats(L); GG:=MatrixGroup<16, K | hh, qq1, qq2, ML[1], ML[2], ML[3], ML[4]>; Order(GG); MGG:=MolienSeries(GG); CROSSREFS Sequence in context: A079289 A048811 A142155 * A048812 A048813 A048814 Adjacent sequences:  A092348 A092349 A092350 * A092352 A092353 A092354 KEYWORD nonn AUTHOR N. J. A. Sloane, Mar 20 2004 STATUS approved

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Last modified February 21 05:23 EST 2020. Contains 332086 sequences. (Running on oeis4.)