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.

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A208028 T(n,k)=Number of nXk 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 0 0 and 1 0 1 vertically.

Original entry on oeis.org

2, 4, 4, 6, 16, 6, 10, 36, 36, 9, 16, 100, 102, 81, 13, 26, 256, 378, 279, 169, 19, 42, 676, 1260, 1377, 741, 361, 28, 68, 1764, 4374, 5895, 4823, 1995, 784, 41, 110, 4624, 14946, 26685, 26845, 17119, 5404, 1681, 60, 178, 12100, 51384, 118179, 158847, 123709
Offset: 1

Views

Author

R. H. Hardin Feb 22 2012

Keywords

Comments

Table starts
..2....4.....6.....10......16.......26........42.........68.........110
..4...16....36....100.....256......676......1764.......4624.......12100
..6...36...102....378....1260.....4374.....14946......51384......176238
..9...81...279...1377....5895....26685....118179.....527913.....2350215
.13..169...741...4823...26845...158847....917293....5349227....31070195
.19..361..1995..17119..123709...955073...7184755...54606513...413322903
.28..784..5404..61292..574560..5788524..56728924..561913408..5542832148
.41.1681.14555.218243.2652823.34901455.445530887.5753550295.73969794325

Examples

			Some solutions for n=4 k=3
..1..1..1....1..0..1....0..1..0....1..1..1....0..1..1....0..1..1....0..1..0
..1..1..1....0..1..1....1..0..1....0..1..0....1..1..0....0..1..1....1..0..0
..1..1..0....0..1..1....1..0..1....0..1..0....0..1..0....1..1..0....1..0..1
..1..0..0....1..0..0....1..1..1....1..0..1....0..1..1....0..1..0....1..1..0
		

Crossrefs

Column 1 is A000930(n+3)
Column 2 is A207170
Row 1 is A006355(n+2)
Row 2 is A206981
Row 3 is A060521

A208501 T(n,k)=Number of nXk 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 1 0 and 1 1 1 vertically.

Original entry on oeis.org

2, 4, 4, 6, 16, 6, 10, 36, 36, 9, 16, 100, 60, 81, 13, 26, 256, 144, 126, 169, 19, 42, 676, 324, 324, 234, 361, 28, 68, 1764, 756, 828, 650, 456, 784, 41, 110, 4624, 1728, 2124, 1794, 1406, 896, 1681, 60, 178, 12100, 3996, 5436, 4992, 4104, 3024, 1722, 3600, 88
Offset: 1

Views

Author

R. H. Hardin Feb 27 2012

Keywords

Comments

Table starts
..2....4....6...10....16....26.....42......68.....110......178......288
..4...16...36..100...256...676...1764....4624...12100....31684....82944
..6...36...60..144...324...756...1728....3996....9180....21168....48708
..9...81..126..324...828..2124...5436...13932...35676....91404...234108
.13..169..234..650..1794..4992..13806...38376..106236...295074...817362
.19..361..456.1406..4104.12654..37430..114494..341012..1037552..3103650
.28..784..896.3024..9912.33488.111328..374416.1249472..4192384.14013664
.41.1681.1722.6150.21976.79376.286754.1037300.3752320.13577396.49125954

Examples

			Some solutions for n=4 k=3
..1..0..0....0..1..1....0..1..0....1..0..0....0..1..0....1..1..0....1..0..1
..1..0..0....1..0..0....1..1..0....0..1..0....0..1..1....1..0..0....1..1..1
..0..1..0....1..1..0....1..0..1....1..1..0....1..0..1....0..1..1....0..1..0
..1..1..0....0..1..1....0..1..1....1..0..0....1..1..0....0..1..1....1..0..1
		

Crossrefs

Column 1 is A000930(n+3)
Column 2 is A207170
Row 1 is A006355(n+2)
Row 2 is A206981
Row 3 is A207590

A208688 T(n,k)=Number of nXk 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 1 1 and 1 0 1 vertically.

Original entry on oeis.org

2, 4, 4, 6, 16, 6, 10, 36, 36, 9, 16, 100, 78, 81, 14, 26, 256, 282, 189, 196, 21, 42, 676, 768, 927, 490, 441, 31, 68, 1764, 2430, 2889, 3430, 1113, 961, 46, 110, 4624, 7086, 11727, 12096, 11067, 2449, 2116, 68, 178, 12100, 21588, 40581, 66094, 41013, 34627
Offset: 1

Views

Author

R. H. Hardin Mar 01 2012

Keywords

Comments

Table starts
..2....4....6.....10.....16......26.......42........68........110.........178
..4...16...36....100....256.....676.....1764......4624......12100.......31684
..6...36...78....282....768....2430.....7086.....21588......64230......193554
..9...81..189....927...2889...11727....40581....154359.....554733.....2062215
.14..196..490...3430..12096...66094...269766...1331988....5795314....27403166
.21..441.1113..11067..41013..301035..1346961...8556723...42184905...249260739
.31..961.2449..34627.133207.1332721..6398617..53340739..290904031..2188890625
.46.2116.5474.111642.444912.6219706.31733422.358035204.2130519946.21086588370

Examples

			Some solutions for n=4 k=3
..1..1..0....0..1..1....0..1..1....0..1..0....0..1..1....1..1..1....1..0..1
..0..1..0....0..1..1....0..1..0....0..1..0....0..1..1....1..1..1....1..1..0
..0..1..0....0..1..1....1..1..0....0..1..1....1..1..0....1..1..1....1..0..0
..1..1..0....0..1..1....0..1..1....1..1..0....0..1..0....0..1..0....1..0..1
		

Crossrefs

Column 1 is A038718(n+2)
Column 2 is A207069
Column 3 is A207724
Row 1 is A006355(n+2)
Row 2 is A206981

Formula

Empirical for row n:
n=1: a(k)=a(k-1)+a(k-2)
n=2: a(k)=2*a(k-1)+2*a(k-2)-a(k-3)
n=3: a(k)=2*a(k-1)+4*a(k-2)-3*a(k-3)
n=4: a(k)=a(k-1)+10*a(k-2)+2*a(k-3)-10*a(k-4)
n=5: a(k)=a(k-1)+17*a(k-2)+4*a(k-3)-32*a(k-4)
n=6: a(k)=a(k-1)+26*a(k-2)+6*a(k-3)-78*a(k-4)
n=7: a(k)=a(k-1)+39*a(k-2)+9*a(k-3)-180*a(k-4)

A221573 T(n,k)=Number of 0..k arrays of length n with each element differing from at least one neighbor by something other than 1.

Original entry on oeis.org

0, 0, 2, 0, 5, 2, 0, 10, 9, 4, 0, 17, 26, 25, 6, 0, 26, 59, 100, 57, 10, 0, 37, 114, 289, 342, 141, 16, 0, 50, 197, 676, 1293, 1210, 345, 26, 0, 65, 314, 1369, 3734, 5913, 4240, 853, 42, 0, 82, 471, 2500, 8991, 20944, 26911, 14898, 2097, 68, 0, 101, 674, 4225, 19014
Offset: 1

Views

Author

R. H. Hardin Jan 20 2013

Keywords

Comments

Table starts
...0.....0.......0........0.........0..........0...........0............0
...2.....5......10.......17........26.........37..........50...........65
...2.....9......26.......59.......114........197.........314..........471
...4....25.....100......289.......676.......1369........2500.........4225
...6....57.....342.....1293......3734.......8991.......19014........36497
..10...141....1210.....5913.....20944......59705......145800.......317233
..16...345....4240....26911....117104.....395641.....1116400......2754635
..26...853...14898...122621....655198....2622817.....8550512.....23923281
..42..2097...52306...558547...3665306...17385993....65485386....207761745
..68..5149..183684..2544357..20505052..115249117...501533796...1804315029
.110.12633..645006.11590169.114711980..763966685..3841097940..15669633131
.178.31013.2264978.52796369.641737294.5064207645.29417832750.136083460405

Examples

			Some solutions for n=6 k=4
..2....2....3....1....0....0....2....1....2....2....3....1....4....3....1....4
..0....0....0....1....4....0....2....3....0....4....0....3....4....3....3....4
..1....1....4....3....4....2....0....4....0....0....4....2....3....0....1....2
..3....1....2....1....3....3....2....4....0....3....3....2....1....3....0....0
..3....4....1....1....0....0....0....3....1....2....1....4....0....3....3....0
..0....1....4....1....3....0....4....0....3....4....3....4....2....3....0....0
		

Crossrefs

Column 1 is A006355
Row 2 is A002522
Row 4 is A082044

Formula

Empirical for column k:
k=1: a(n) = a(n-1) +a(n-2)
k=2: a(n) = 3*a(n-1) -2*a(n-2) +4*a(n-4)
k=3: a(n) = 3*a(n-1) +2*a(n-2) -a(n-3) +a(n-4)
k=4: a(n) = 5*a(n-1) -3*a(n-2) +a(n-3) +15*a(n-4) +3*a(n-5) for n>6
k=5: a(n) = 5*a(n-1) +3*a(n-2) +9*a(n-4) +6*a(n-5) +3*a(n-6)
k=6: a(n) = 7*a(n-1) -4*a(n-2) +6*a(n-3) +26*a(n-4) +10*a(n-5) +16*a(n-6) +12*a(n-8)
k=7: a(n) = 7*a(n-1) +4*a(n-2) +5*a(n-3) +20*a(n-4) +20*a(n-5) +23*a(n-6) -6*a(n-7) +3*a(n-8)
Empirical for row n:
n=2: a(n) = 1*n^2 + 1
n=3: a(n) = 1*n^3 - 1*n^2 + 3*n - 1
n=4: a(n) = 1*n^4 + 2*n^2 + 1
n=5: a(n) = 1*n^5 + 1*n^4 - 2*n^3 + 12*n^2 - 15*n + 9 for n>2
n=6: a(n) = 1*n^6 + 2*n^5 - 5*n^4 + 24*n^3 - 41*n^2 + 50*n - 31 for n>3
n=7: a(n) = 1*n^7 + 3*n^6 - 7*n^5 + 29*n^4 - 41*n^3 + 45*n^2 - 33*n + 19 for n>2

A052995 Expansion of 2*x*(1 - x)/(1 - 3*x + x^2).

Original entry on oeis.org

0, 2, 4, 10, 26, 68, 178, 466, 1220, 3194, 8362, 21892, 57314, 150050, 392836, 1028458, 2692538, 7049156, 18454930, 48315634, 126491972, 331160282, 866988874, 2269806340, 5942430146, 15557484098, 40730022148, 106632582346, 279167724890, 730870592324
Offset: 0

Views

Author

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

Keywords

Comments

Terms >=4 give solutions x to floor(phi^2*x^2) - floor(phi*x)^2 = 5, where phi =(1 + sqrt(5))/2. - Benoit Cloitre, Mar 16 2003
Except for the first term, positive values of x (or y) satisfying x^2 - 18*x*y + y^2 + 256 = 0. - Colin Barker, Feb 14 2014
a(n+1) is the square of the distance AB, where A is the point (F(n), F(n+1)), B is the 90-degree rotation of A about the origin, and F(n)=A000045(n) are the Fibonacci numbers. - Burak Muslu, Mar 24 2021

References

  • A. T. Benjamin and J. J. Quinn, Proofs that really count: the art of combinatorial proof, M.A.A. 2003, id. 30.
  • B. Muslu, Sayılar ve Bağlantılar 2, Luna, 2021, pages 60-61.

Crossrefs

Bisection of A006355.
First differences of A025169.

Programs

  • Maple
    spec := [S, S=Prod(Sequence(Union(Prod(Sequence(Z),Z),Z)),Union(Z,Z))},unlabeled ]: seq(combstruct[count ](spec,size=n), n=0..20);
  • Mathematica
    LinearRecurrence[{3, -1}, {0, 2, 4}, 30] (* or *)
    Nest[Append[#, 3 #[[-1]] - #[[-2]]] &, {0, 2, 4}, 27] (* or *)
    CoefficientList[Series[-2 x (-1 + x)/(1 - 3 x + x^2), {x, 0, 29}], x] (* Michael De Vlieger, Jul 18 2018 *)
  • PARI
    concat(0, Vec(2*x*(1-x)/(1-3*x+x^2) + O(x^50))) \\ Colin Barker, Mar 30 2016
    
  • PARI
    a(n) = fibonacci(max(0,2*n-1))<<1; \\ Kevin Ryde, Mar 25 2021

Formula

G.f.: -2*x*(-1 + x)/(1 - 3*x + x^2).
a(0) = 0, a(1) = 2, a(2) = 4; for n > 0, a(n) - 3*a(n+1) + a(n+2) = 0.
a(n) = A069403(n-1)+1.
a(n) = Sum(2/5*(-1 + 4*_alpha)*_alpha^(-1-n), _alpha = RootOf(_Z^2 - 3*_Z + 1)).
a(n) = 2*Fibonacci(2*n-1) = 2*A001519(n) for n > 0. - Vladeta Jovovic, Mar 19 2003
a(n+2) = F(n)^2 + F(n+3)^2 = 2*F(n+1)^2 + 2*F(n+2)^2, where F = A000045. - N. J. A. Sloane, Feb 20 2005
a(n) = 1/2*(F(2*n+8) mod F(2*n+2)) for n > 2. - Gary Detlefs, Nov 22 2010
a(n) = F(n-3)*F(n-1) + F(n)*F(n+2) for n > 0, F(-2) = -1, F(-1) = 1. - Bruno Berselli, Nov 03 2015
a(n) = (2^(-n)*((3 - sqrt(5))^n*(1 + sqrt(5)) + (-1 + sqrt(5))*(3 + sqrt(5))^n))/sqrt(5) for n > 0. - Colin Barker, Mar 30 2016
a(n) = Fibonacci(2*n-2) + Lucas(2*n-2) for n > 0. - Bruno Berselli, Oct 13 2017
a(n) = Lucas(2*n) - Fibonacci(2*n) for n > 0. - Diego Rattaggi, Mar 08 2023

Extensions

More terms from James Sellers, Jun 05 2000

A207774 T(n,k)=Number of nXk 0..1 arrays avoiding 0 0 0 and 1 1 1 horizontally and 0 0 1 and 0 1 0 vertically.

Original entry on oeis.org

2, 4, 4, 6, 16, 6, 10, 36, 36, 9, 16, 100, 84, 81, 14, 26, 256, 292, 192, 196, 21, 42, 676, 912, 828, 450, 441, 31, 68, 1764, 2812, 3130, 2514, 972, 961, 46, 110, 4624, 8928, 11230, 11950, 7164, 2040, 2116, 68, 178, 12100, 28152, 43260, 49122, 43264, 20104
Offset: 1

Views

Author

R. H. Hardin Feb 20 2012

Keywords

Comments

Table starts
..2....4....6....10.....16......26.......42........68........110.........178
..4...16...36...100....256.....676.....1764......4624......12100.......31684
..6...36...84...292....912....2812.....8928.....28152......87972......277292
..9...81..192...828...3130...11230....43260....163710.....604340.....2295512
.14..196..450..2514..11950...49122...240346...1128862....4877154....23327018
.21..441..972..7164..43264..195160..1246206...7381202...35627804...220514498
.31..961.2040.20104.157472..759482..6513576..49975640..259077468..2150453548
.46.2116.4278.57458.597090.3023026.35632160.364308938.1972417684.22562076620

Examples

			Some solutions for n=4 k=3
..0..1..1....1..1..0....1..0..0....1..1..0....0..1..0....0..0..1....1..1..0
..1..1..0....1..1..0....0..1..1....1..1..0....1..0..0....1..1..0....0..0..1
..1..1..0....1..1..0....0..1..1....0..1..0....1..1..0....1..1..0....0..1..1
..1..0..0....1..1..0....0..0..1....0..1..0....0..1..0....0..1..0....0..1..1
		

Crossrefs

Column 1 is A038718(n+2)
Column 2 is A207069
Row 1 is A006355(n+2)
Row 2 is A206981
Row 3 is A207341
Row 4 is A207342

A207808 T(n,k)=Number of nXk 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 1 0 and 1 0 1 vertically.

Original entry on oeis.org

2, 4, 4, 6, 16, 6, 10, 36, 36, 10, 16, 100, 102, 100, 16, 26, 256, 378, 370, 256, 26, 42, 676, 1260, 1970, 1232, 676, 42, 68, 1764, 4374, 9040, 9168, 4238, 1764, 68, 110, 4624, 14946, 43990, 57184, 44538, 14406, 4624, 110, 178, 12100, 51384, 209050, 382288
Offset: 1

Views

Author

R. H. Hardin Feb 20 2012

Keywords

Comments

Table starts
..2....4.....6......10.......16........26.........42..........68...........110
..4...16....36.....100......256.......676.......1764........4624.........12100
..6...36...102.....378.....1260......4374......14946.......51384........176238
.10..100...370....1970.....9040.....43990.....209050.....1002960.......4793390
.16..256..1232....9168....57184....382288....2485392....16340928.....106947696
.26..676..4238...44538...379444...3511534...31431114...285153752....2572767886
.42.1764.14406..212814..2472540..31569510..388134978..4844843724...60105117534
.68.4624.49164.1022652.16206848.285774964.4829044276.82999241712.1416863447084

Examples

			Some solutions for n=4 k=3
..0..1..0....0..1..1....0..1..0....1..0..0....1..1..0....1..1..0....0..1..1
..0..1..1....1..1..0....0..1..1....0..1..1....1..1..0....0..1..0....0..1..1
..0..1..1....1..1..0....1..1..1....0..1..1....1..0..0....0..1..1....0..1..0
..0..1..0....0..1..0....1..0..0....1..1..1....1..0..1....1..0..1....0..1..0
		

Crossrefs

Column 1 is A006355(n+2)
Column 2 is A206981
Column 3 is A207249
Row 1 is A006355(n+2)
Row 2 is A206981
Row 3 is A060521

A207858 T(n,k)=Number of nXk 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 1 0 and 1 0 1 vertically.

Original entry on oeis.org

2, 4, 4, 6, 16, 6, 9, 36, 36, 10, 15, 81, 102, 100, 16, 25, 225, 289, 370, 256, 26, 40, 625, 1071, 1369, 1232, 676, 42, 64, 1600, 3969, 7289, 5929, 4238, 1764, 68, 104, 4096, 13230, 38809, 44121, 26569, 14406, 4624, 110, 169, 10816, 44100, 178088, 328329
Offset: 1

Views

Author

R. H. Hardin Feb 21 2012

Keywords

Comments

Table starts
..2....4.....6......9.......15........25.........40..........64...........104
..4...16....36.....81......225.......625.......1600........4096.........10816
..6...36...102....289.....1071......3969......13230.......44100........153090
.10..100...370...1369.....7289.....38809.....178088......817216.......3976696
.16..256..1232...5929....44121....328329....2047902....12773476......85393582
.26..676..4238..26569...279219...2934369...24999522...212984836....1971051046
.42.1764.14406.117649..1737981..25674489..298294290..3465676900...44249929850
.68.4624.49164.522729.10873197.226171521.3584335104.56804048896.1001624438528

Examples

			Some solutions for n=4 k=3
..0..1..1....0..0..1....0..1..1....0..0..1....0..1..1....1..1..1....0..0..1
..0..1..1....0..1..1....1..1..0....0..0..1....1..0..0....1..1..0....0..0..1
..0..1..1....0..1..1....1..1..0....1..0..1....1..0..0....1..0..0....1..1..1
..0..1..1....0..1..1....1..0..1....1..0..0....1..1..0....1..0..1....1..1..0
		

Crossrefs

Column 1 is A006355(n+2)
Column 2 is A206981
Column 3 is A207249
Row 1 is A006498(n+2)
Row 2 is A189145(n+2)
Row 3 is A207704

A207895 T(n,k)=Number of nXk 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 0 0 and 1 1 1 vertically.

Original entry on oeis.org

2, 4, 4, 6, 16, 6, 9, 36, 36, 10, 13, 81, 84, 100, 16, 19, 169, 198, 292, 256, 26, 28, 361, 462, 870, 912, 676, 42, 41, 784, 1080, 2446, 3358, 2812, 1764, 68, 60, 1681, 2520, 6952, 11196, 12040, 8928, 4624, 110, 88, 3600, 5886, 20168, 38160, 49442, 47320, 28152
Offset: 1

Views

Author

R. H. Hardin Feb 21 2012

Keywords

Comments

Table starts
..2....4.....6......9......13......19.......28........41.........60.........88
..4...16....36.....81.....169.....361......784......1681.......3600.......7744
..6...36....84....198.....462....1080.....2520......5886......13746......32100
.10..100...292....870....2446....6952....20168.....57838.....164914.....473632
.16..256...912...3358...11196...38160...135714....471374....1605156....5575548
.26..676..2812..12040...49442..205258...856480...3559040...14795830...61589756
.42.1764..8928..47320..231900.1153532..5888458..29719004..148308700..747498440
.68.4624.28152.182192.1070030.6420722.39828558.243318702.1460399404.8907998820

Examples

			Some solutions for n=4 k=3
..1..1..1....0..1..1....1..1..1....1..1..1....0..0..1....0..1..1....1..0..0
..1..1..0....1..0..0....1..1..0....0..0..1....0..1..1....0..0..1....1..1..1
..0..0..1....1..0..0....0..0..1....0..1..0....1..1..0....1..1..0....0..1..0
..0..1..1....0..1..1....1..1..0....1..0..0....0..0..1....0..0..1....1..0..0
		

Crossrefs

Column 1 is A006355(n+2)
Column 2 is A206981
Column 3 is A207341
Column 4 is A207662
Row 1 is A000930(n+3)
Row 2 is A207170

A207918 T(n,k)=Number of nXk 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 1 0 and 1 0 1 vertically.

Original entry on oeis.org

2, 4, 4, 6, 16, 6, 9, 36, 36, 10, 13, 81, 98, 100, 16, 19, 169, 271, 358, 256, 26, 28, 361, 665, 1309, 1152, 676, 42, 41, 784, 1675, 4181, 5371, 3910, 1764, 68, 60, 1681, 4344, 13759, 21145, 23637, 12994, 4624, 110, 88, 3600, 11081, 46800, 86255, 117835
Offset: 1

Views

Author

R. H. Hardin Feb 21 2012

Keywords

Comments

Table starts
..2....4.....6......9......13.......19........28.........41..........60
..4...16....36.....81.....169......361.......784.......1681........3600
..6...36....98....271.....665.....1675......4344......11081.......28136
.10..100...358...1309....4181....13759.....46800.....156135......518564
.16..256..1152...5371...21145....86255....366330....1520815.....6276388
.26..676..3910..23637..117835...612439...3327954...17621905....92785236
.42.1764.12994.101069..628945..4105063..28188778..187980955..1245595210
.68.4624.43596.438103.3426491.28280693.247024548.2088382007.17532981294

Examples

			Some solutions for n=4 k=3
..1..1..1....1..1..0....0..0..1....1..1..0....1..1..1....0..0..1....0..0..1
..1..1..1....0..0..1....0..0..1....1..0..0....1..1..1....0..1..1....1..0..0
..0..1..0....0..0..1....0..0..1....1..0..0....1..1..1....0..1..0....1..1..0
..0..1..0....1..0..0....1..1..1....0..1..1....1..1..1....0..1..0....0..1..1
		

Crossrefs

Column 1 is A006355(n+2)
Column 2 is A206981
Column 3 is A207462
Row 1 is A000930(n+3)
Row 2 is A207170
Row 3 is A207306
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