cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-7 of 7 results.

A008621 Expansion of 1/((1-x)*(1-x^4)).

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 19, 19, 19, 19, 20, 20, 20, 20, 21, 21
Offset: 0

Views

Author

Keywords

Comments

Arises from Gleason's theorem on self-dual codes: 1/((1-x^2)*(1-x^8)) is the Molien series for the real 2-dimensional Clifford group (a dihedral group of order 16) of genus 1.
Thickness of the hypercube graph Q_n. - Eric W. Weisstein, Sep 09 2008
Count of odd numbers between consecutive quarter-squares, A002620. Oppermann's conjecture states that for each count there will be at least one prime. - Fred Daniel Kline, Sep 10 2011
Number of partitions into parts 1 and 4. - Joerg Arndt, Jun 01 2013
a(n-1) is the minimum independence number over all planar graphs with n vertices. The bound follows from the Four Color Theorem. It is attained by a union of 4-cliques. Other extremal graphs are examined in the Bickle link. - Allan Bickle, Feb 04 2022

References

  • D. J. Benson, Polynomial Invariants of Finite Groups, Cambridge, 1993, p. 100.
  • F. J. MacWilliams and N. J. A. Sloane, Theory of Error-Correcting Codes, 1977, Chapter 19, Problem 3, p. 602.

Crossrefs

Cf. A002265 (equals this - 1).

Programs

Formula

a(n) = floor(n/4) + 1.
a(n) = A010766(n+4, 4).
Also, a(n) = ceiling((n+1)/4), n >= 0. - Mohammad K. Azarian, May 22 2007
a(n) = Sum_{i=0..n} A121262(i) = n/4 + 5/8 + (-1)^n/8 + A057077(n)/4. - R. J. Mathar, Mar 14 2011
a(x,y) := floor(x/2) + floor(y/2) - x where x = A002620(n) and y = A002620(n+1), n > 2. - Fred Daniel Kline, Sep 10 2011
a(n) = a(n-1) + a(n-4) - a(n-5); a(0)=1, a(1)=1, a(2)=1, a(3)=1, a(4)=2. - Harvey P. Dale, Feb 19 2012
From R. J. Mathar, Jun 04 2021: (Start)
G.f.: 1 / ( (1+x)*(1+x^2)*(x-1)^2 ).
a(n) + a(n-1) = A004524(n+3).
a(n) + a(n-2) = A008619(n). (End)
a(n) = A002265(n) + 1. - M. F. Hasler, Oct 17 2022

Extensions

More terms from Stefan Steinerberger, Apr 03 2006

A024186 Expansion of Molien series for 8-dimensional real Clifford group 2^{1+6}.Alt_8.2 of genus 3 and order 5160960.

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 3, 4, 6, 7, 10, 12, 18, 22, 29, 35, 48, 57, 74, 91, 116, 140, 177, 211, 265, 319, 389, 462, 566, 667, 804, 949, 1131, 1324, 1573, 1827, 2153, 2502, 2917, 3364, 3916, 4491, 5187, 5937, 6813, 7760, 8879, 10058, 11448, 12950, 14658, 16500, 18632, 20894
Offset: 0

Views

Author

N. J. A. Sloane, G. Nebe (nebe(AT)math.rwth-aachen.de)

Keywords

Crossrefs

Programs

  • Magma
    // Commands to generate the group.
    F := QuadraticField(2); M := GeneralLinearGroup(8, F); t := 1/(2*s);
    B := M! [ -t, -t, -t, -t, -t, -t, -t, -t,
    -t, t, -t, -t, t, -t, t, t,
    -t, -t, -t, t, -t, t, t, t,
    -t, -t, t, -t, t, t, t, -t,
    -t, t, -t, t, t, t, -t, -t,
    -t, -t, t, t, t, -t, -t, t,
    -t, t, t, t, -t, -t, t, -t,
    -t, t, t, -t, -t, t, -t, t ];
    S := M! [ -1, 0, 0, 0, 0, 0, 0, 0,
    0, -1, 0, 0, 0, 0, 0, 0,
    0, 0, 1, 0, 0, 0, 0, 0,
    0, 0, 0, 1, 0, 0, 0, 0,
    0, 0, 0, 0, 1, 0, 0, 0,
    0, 0, 0, 0, 0, 1, 0, 0,
    0, 0, 0, 0, 0, 0, 1, 0,
    0, 0, 0, 0, 0, 0, 0, 1 ];
    C := M! [ 1, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 1, 0, 0, 0, 0, 0,
    0, 0, 0, 1, 0, 0, 0, 0,
    0, 0, 0, 0, 1, 0, 0, 0,
    0, 0, 0, 0, 0, 1, 0, 0,
    0, 0, 0, 0, 0, 0, 1, 0,
    0, 0, 0, 0, 0, 0, 0, 1,
    0, 1, 0, 0, 0, 0, 0, 0 ];
    G := sub< M | B, S, C >; Order(G);
  • Mathematica
    ker = {1, 0, 1, -1, 0, 0, 1, 0, -1, -1, 0, 3, -2, 0, -2, 2, 0, 0, -2, 1, 1, 1, -1, -1, 2, 0, -1, -1, 1, 2, 0, -3, 0, 2, 2, -3, -2, 0, 4, 0, -2, -3, 2, 2, 0, -3, 0, 2, 1, -1, -1, 0, 2, -1, -1, 1, 1, 1, -2, 0, 0, 2, -2, 0, -2, 3, 0, -1, -1, 0, 1, 0, 0, -1, 1, 0, 1, -1};
    init = {1, 1, 1, 1, 2, 2, 3, 4, 6, 7, 10, 12, 18, 22, 29, 35, 48, 57, 74, 91, 116, 140, 177, 211, 265, 319, 389, 462, 566, 667, 804, 949, 1131, 1324, 1573, 1827, 2153, 2502, 2917, 3364, 3916, 4491, 5187, 5937, 6813, 7760, 8879, 10058, 11448, 12950, 14658, 16500, 18632, 20894, 23487, 26279, 29417, 32801, 36630, 40695, 45285, 50223, 55690, 61559, 68119, 75092, 82841, 91141, 100256, 110026, 120800, 132226, 144804, 158251, 172881, 188489, 205560, 223657};
    LinearRecurrence[ker, init, 1000] (* Jean-François Alcover, Jan 05 2020 *)

Formula

Molien series = (t^148 - t^142 + t^140 + t^136 - t^134 + t^132 + 3*t^128 + 2*t^124 + 4*t^120 + 5*t^116 + 7*t^112 + t^110 + 7*t^108 + t^106 + 10*t^104 + 2*t^102 + 11*t^100 + 3*t^98 + 12*t^96 + 4*t^94 + 14*t^92 + 5*t^90 + 16*t^88 + 5*t^86 + 15*t^84 + 4*t^82 + 20*t^80 + 7*t^78 + 18*t^76 + 4*t^74 + 18*t^72 + 7*t^70 + 20*t^68 + 4*t^66 + 15*t^64 + 5*t^62 + 16*t^60 + 5*t^58 + 14*t^56 + 4*t^54 + 12*t^52 + 3*t^50 + 11*t^48 + 2*t^46 + 10*t^44 + t^42 + 7*t^40 + t^38 + 7*t^36 + 5*t^32 + 4*t^28 + 2*t^24 + 3*t^20 + t^16 - t^14 + t^12 + t^8 - t^6 + 1) /
(t^156 - t^154 - t^150 + t^148 - t^142 + t^138 + t^136 - 3*t^132 + 2*t^130 + 2*t^126 - 2*t^124 + 2*t^118 - t^116 - t^114 - t^112 + t^110 + t^108 - 2*t^106 + t^102 + t^100 - t^98 - 2*t^96 + 3*t^92 - 2*t^88 - 2*t^86 + 3*t^84 + 2*t^82 - 4*t^78 + 2*t^74 + 3*t^72 - 2*t^70 - 2*t^68 + 3*t^64 - 2*t^60 - t^58 + t^56 + t^54 - 2*t^50 + t^48 + t^46 - t^44 - t^42 - t^40 + 2*t^38 - 2*t^32 + 2*t^30 + 2*t^26 - 3*t^24 + t^20 + t^18 - t^14 + t^8 - t^6 - t^2 + 1).

Extensions

Rechecked Mar 30 2004. There were errors in the formula line, although not in the sequence itself.

A028288 Molien series for complex 4-dimensional Clifford group of order 92160 and genus 2. Also Molien series of ring of biweight enumerators of Type II self-dual binary codes.

Original entry on oeis.org

1, 1, 1, 3, 4, 5, 8, 10, 12, 17, 21, 24, 31, 37, 42, 52, 60, 67, 80, 91, 101, 117, 131, 144, 164, 182, 198, 222, 244, 264, 293, 319, 343, 377, 408, 437, 476, 512, 546, 591, 633, 672, 723, 771, 816, 874, 928, 979, 1044, 1105, 1163, 1235, 1303, 1368
Offset: 0

Keywords

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Integers(), 60); Coefficients(R!( (1+x^4)/((1-x)*(1-x^3)^2*(1-x^5)) )); // G. C. Greubel, Feb 01 2020
    
  • Maple
    seq(coeff(series((1+x^4)/((1-x)*(1-x^3)^2*(1-x^5)), x, n+1), x, n), n = 0..60); # G. C. Greubel, Feb 01 2020
  • Mathematica
    LinearRecurrence[{1,0,2,-2,1,-2,1,-2,2,0,1,-1}, {1,1,1,3,4,5,8,10,12,17,21,24}, 60] (* Jean-François Alcover, Jan 27 2015 *)
    CoefficientList[Series[(1+x^4)/((1-x)(1-x^3)^2(1-x^5)),{x,0,60}],x] (* Harvey P. Dale, Jul 10 2019 *)
  • PARI
    Vec((1+x^4)/((1-x)*(1-x^3)^2*(1-x^5)) + O('x^60)) \\ G. C. Greubel, Feb 01 2020
    
  • Sage
    def A028288_list(prec):
        P. = PowerSeriesRing(ZZ, prec)
        return P( (1+x^4)/((1-x)*(1-x^3)^2*(1-x^5)) ).list()
    A028288_list(60) # G. C. Greubel, Feb 01 2020

Formula

G.f.: (1+x^4)/((1-x)*(1-x^3)^2*(1-x^5)).
a(n) ~ 1/135*n^3. - Ralf Stephan, Apr 29 2014

A039946 Expansion of Molien series for 8-dimensional complex Clifford group of genus 3 and order 743178240.

Original entry on oeis.org

1, 1, 2, 5, 9, 16, 31, 53, 89, 152, 245, 384, 601, 911, 1351, 1986, 2856, 4037, 5653, 7791, 10592, 14268, 18990, 24999, 32643, 42218, 54112, 68869, 86971, 109014, 135812, 168101, 206769, 252990, 307849, 372616, 448934, 538348
Offset: 0

Author

E. M. Rains

Keywords

Examples

			G.f. = 1 + x^8 + 2*x^16 + 5*x^24 + 9*x^32 + 16*x^40 + 31*x^48 + ...
		

Crossrefs

Programs

  • Maple
    f(x):= (1 +x^3 +3*x^4 +3*x^5 +6*x^6 +8*x^7 +12*x^8 +18*x^9 +25*x^10 +29*x^11 +40*x^12 +50*x^13 +58*x^14 +69*x^15 +80*x^16 +85*x^17 +96*x^18 +104*x^19 +107*x^20 +109*x^21 +112*x^22 +109*x^23+107*x^24 +104*x^25 +96*x^26 +85*x^27 +80*x^28 +69*x^29 +58*x^30 +50*x^31 +40*x^32 +29*x^33 +25*x^34 +18*x^35 +12*x^36 +8*x^37 +6*x^38 +3*x^39 +3*x^40 +x^41 +x^44) / ( (1-x)^2*(1-x^3)^4*(1-x^5)^2*(1 +x +2*x^3 +2*x^4 + x^5 +4*x^6 +2*x^7 +x^8 +5*x^9 +2*x^10 +2*x^11 +5*x^12 +x^13 +2*x^14 + 4*x^15 +x^16 +2*x^17 +2*x^18 +x^20 +x^21) ); seq(coeff(series(f(x), x, n+1), x, n), n = 0..40);
  • Mathematica
    CoefficientList[Series[(1+x^3+3*x^4+3*x^5+6*x^6+8*x^7+12*x^8+18*x^9+25*x^10 + 29*x^11+40*x^12+50*x^13+58*x^14+69*x^15+80*x^16+85*x^17+96*x^18+104*x^19 + 107*x^20+109*x^21+112*x^22+109*x^23+107*x^24+104*x^25+96*x^26+85*x^27+80*x^28 +69*x^29+58*x^30+50*x^31+40*x^32+29*x^33+25*x^34+18*x^35+12*x^36 + 8*x^37 + 6*x^38+3*x^39+3*x^40+x^41+x^44)/((1-x)^2*(1-x^3)^4*(1-x^5)^2*(1+x+2*x^3+2*x^4 +x^5+4*x^6+2*x^7+x^8+5*x^9+2*x^10+2*x^11+5*x^12+x^13+2*x^14+4*x^15+x^16+2*x^17 +2*x^18+x^20+x^21)), {x,0,40}], x] (* G. C. Greubel, Feb 01 2020 *)
    LinearRecurrence[{1,1,1,-2,-1,0,1,-1,1,0,0,-1,1,2,1,-3,-2,0,2,1,-1,0,0,-1,1,2,0,-2,-3,1,2,1,-1,0,0,1,-1,1,0,-1,-2,1,1,1,-1},{1,1,2,5,9,16,31,53,89,152,245,384,601,911,1351,1986,2856,4037,5653,7791,10592,14268,18990,24999,32643,42218,54112,68869,86971,109014,135812,168101,206769,252990,307849,372616,448934,538348,642630,764021,904658,1066943,1253876,1468340,1713529},40] (* Harvey P. Dale, Jul 04 2021 *)

Formula

G.f.: (1 +x^24 +3*x^32 +3*x^40 +6*x^48 +8*x^56 +12*x^64 +18*x^72 +25*x^80 +29*x^88 +40*x^96 +50*x^104 +58*x^112 +69*x^120 +80*x^128 +85*x^136 +96*x^144 +104*x^152 +107*x^160 +109*x^168 +112*x^176 +109*x^184 +107*x^192 +104*x^200 +96*x^208 +85*x^216 +80*x^224 +69*x^232 +58*x^240 +50*x^248 +40*x^256 +29*x^264 +25*x^272 +18*x^280 +12*x^288 +8*x^296 +6*x^304 +3*x^312 +3*x^320 +x^328 +x^352) / ( (1-x^8)^2*(1-x^24)^4*(1-x^40)^2*(1 +x^8 +2*x^24 +2*x^32 + x^40 +4*x^48 +2*x^56 +x^64 +5*x^72 +2*x^80 +2*x^88 +5*x^96 +x^104 +2*x^112 + 4*x^120 +x^128 +2*x^136 +2*x^144 +x^160 +x^168) ), nonzero terms.
G.f.: (1 +x^3 +3*x^4 +3*x^5 +6*x^6 +8*x^7 +12*x^8 +18*x^9 +25*x^10 +29*x^11 +40*x^12 +50*x^13 +58*x^14 +69*x^15 +80*x^16 +85*x^17 +96*x^18 +104*x^19 +107*x^20 +109*x^21 +112*x^22 +109*x^23+107*x^24 +104*x^25 +96*x^26 +85*x^27 +80*x^28 +69*x^29 +58*x^30 +50*x^31 +40*x^32 +29*x^33 +25*x^34 +18*x^35 +12*x^36 +8*x^37 +6*x^38 +3*x^39 +3*x^40 +x^41 +x^44) / ( (1-x)^2*(1-x^3)^4*(1-x^5)^2*(1 +x +2*x^3 +2*x^4 + x^5 +4*x^6 +2*x^7 +x^8 +5*x^9 +2*x^10 +2*x^11 +5*x^12 +x^13 +2*x^14 + 4*x^15 +x^16 +2*x^17 +2*x^18 +x^20 +x^21) ). - G. C. Greubel, Feb 01 2020

Extensions

Typo in reduced g.f.s. corrected by Georg Fischer, Apr 18 2020

A051354 Expansion of Molien series for 16-dimensional complex Clifford group of genus 4 and order 97029351014400.

Original entry on oeis.org

1, 1, 2, 7, 19, 52, 172, 550, 1782, 5845, 18508, 56345, 164157, 454518, 1196924, 3003750, 7198311, 16523847, 36447873, 77478005, 159172517, 316874035, 612729396, 1153359711, 2117566545, 3798941401, 6670327291, 11479693332, 19390588953, 32185179449, 52553840336
Offset: 0

Keywords

Comments

Oura gives an explicit formula for the Molien series that produces A027672; the present sequence is the subsequence formed from the terms whose exponents are multiples of 8 (that is, every other term of A027672). In other words, the present Molien series is (f(x)+f(z*x))/2, where z = exp(2*Pi*I/8) and f(x) is the Molien series for the group H_4 given explicitly by Oura in Theorem 4.1.

Examples

			1 + t^8 + 2*t^16 + 7*t^24 + 19*t^32 + 52*t^40 + 172*t^48 + ...
		

Programs

  • Mathematica
    (* See link for Mathematica program. *)

Formula

a(n) = A027672(2*n).

Extensions

Edited by Georg Fischer, Jan 24 2021

A097913 G.f.: (1+x^18)/((1-x)*(1-x^8)*(1-x^12)*(1-x^24)).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 5, 5, 6, 6, 6, 6, 9, 9, 10, 10, 11, 11, 12, 12, 15, 15, 16, 16, 19, 19, 20, 20, 23, 23, 26, 26, 29, 29, 30, 30, 36, 36, 39, 39, 42, 42, 45, 45, 51, 51, 54, 54, 60, 60, 63, 63, 69, 69, 75, 75, 81, 81, 84, 84, 94, 94, 100, 100, 106, 106
Offset: 0

Author

N. J. A. Sloane, Sep 04 2004

Keywords

Comments

Conjectured Poincaré series [or Poincare series] for genus 2 Siegel theta series of odd unimodular lattices.

Crossrefs

Cf. A008718.

Programs

  • Mathematica
    CoefficientList[Series[(1 + x^18)/((1 - x)*(1 - x^8)*(1 - x^12)*(1 - x^24)), {x, 0, 50}], x] (* G. C. Greubel, Dec 20 2017 *)
  • PARI
    x='x+O('x^30); Vec((1+x^18)/((1-x)*(1-x^8)*(1-x^12)*(1-x^24))) \\ G. C. Greubel, Dec 20 2017

A110868 Molien series for real 32-dimensional Clifford group of genus 5 and order 96253116206284800.

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 3, 3, 3, 4, 7, 9, 16, 23, 46, 74
Offset: 0

Author

G. Nebe, Sep 21 2005

Keywords

Crossrefs

Cf. A008621, A008718, A024186, A110160, this sequence, A110869, A110876, A110880. See also A001309.
Showing 1-7 of 7 results.