A002502 -id:A002502 - cp's OEIS frontend

A002501 a(n) = 7^n - 34^n + 23^n.

1, 19, 205, 1795, 14221, 106819, 778765, 5581315, 39606541, 279447619, 1965098125, 13792018435, 96690872461, 677427332419, 4744368982285, 33220131761155, 232579232659981, 1628208214321219, 11398072876175245, 79788974736297475, 558532690864457101

Offset: 1

N. J. A. Sloane

Counts connected relations. On page 578 Kreweras (1969) says: "Le théorème s'applique notamment au dénombrement des relations binaires externes qui possèdent la propriété de connexité; cela revient à calculer le nombre a(m,n) de manières de remplir un tableau de m lignes et n colonnes avec des 0 et des 1, en respectant les deux conditions suivantes: (1): aucune rangée (ligne ni colonne) ne doit être tout entière remplie de zéros; (2): deux cases quelconques marquées 1 peuvent être jointes par une chaîne de cases marquées 1 telle que deux cases consécutives de la chaîne appartiennent à une même rangée."

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

T. D. Noe, Table of n, a(n) for n = 1..200
G. Kreweras, Inversion des polynomes de Bell bidimensionnels et application au dénombrement des relations binaires connexes, C. R. Acad. Sci. Paris Ser. A-B 268 1969 A577-A579.
Index entries for linear recurrences with constant coefficients, signature (14,-61,84)

Cf. A005333, A001047, A002502, A093732, A093733.

A diagonal of A262307.

Table[7^n - 3*4^n + 2*3^n, {n, 20}] (* T. D. Noe, May 29 2012 *)

a(n)=7^n-3*4^n+2*3^n \\ Charles R Greathouse IV, Sep 24 2015

G.f.: -x*(1+5*x) / ( (3*x-1)*(7*x-1)*(4*x-1) ). - R. J. Mathar, Jun 09 2013

a(n) = 14*a(n-1) - 61*a(n-2) + 84*a(n-3). - Wesley Ivan Hurt, Apr 11 2022

Better definition and more terms from Goran Kilibarda, Vladeta Jovovic, Apr 14 2004

A093732 Number of connected relations.

Original entry on oeis.org

1, 211, 14221, 636331, 23679901, 805351531, 26175881341, 831358677451, 26094426008221, 814105545191851, 25320182311228861, 786251347986776971, 24394981288950302941, 756583120577782494571, 23459491617092461686781, 727330825918603925122891

Offset: 1

Goran Kilibarda, Vladeta Jovovic, Apr 14 2004

T. D. Noe, Table of n, a(n) for n = 1..200
G. Kilibarda and V. Jovovic, Enumeration of some classes of T_0-hypergraphs, arXiv:1411.4187 [math.CO], 2014.
G. Kreweras, Inversion des polynômes de Bell bidimensionnels et application au dénombrement des relations binaires connexes, C. R. Acad. Sci. Paris Ser. A-B 268 1969 A577-A579.
Index entries for linear recurrences with constant coefficients, signature (84,-2774,47548,-462525,2575088,-7643820,9374400).

Cf. A005333, A001047, A002501, A002502, A093733.

Table[31^n - 5*16^n - 10*10^n + 20*9^n + 30*7^n - 60*6^n + 24*5^n, {n, 25}] (* T. D. Noe, May 29 2012 *)

a(n)=31^n-5*16^n-10*10^n+20*9^n+30*7^n-60*6^n+24*5^n \\ Charles R Greathouse IV, Jun 16 2015

a(n) = 31^n - 5*16^n - 10*10^n + 20*9^n + 30*7^n - 60*6^n + 24*5^n.

G.f.: -x*(1+127*x-729*x^2-20467*x^3+107048*x^4+259620*x^5) / ( (9*x-1)*(6*x-1)*(7*x-1)*(5*x-1)*(31*x-1)*(10*x-1)*(16*x-1) ). - R. J. Mathar, Jun 09 2013

A093733 Number of connected relations.

Original entry on oeis.org

1, 665, 106819, 10365005, 805351531, 56294206205, 3735873535339, 241600284318365, 15423235216318411, 978180744322139645, 61834480769377286059, 3902270609960140639325, 246057483524862034206091, 15508484277325946034039485, 977254123876968508188975979

Offset: 1

Goran Kilibarda and Vladeta Jovovic, Apr 14 2004

T. D. Noe, Table of n, a(n) for n = 1..100
Goran Kilibarda and Vladeta Jovovic, Enumeration of some classes of T_0-hypergraphs, arXiv:1411.4187 [math.CO], 2014.
G. Kreweras, Inversion des polynômes de Bell bidimensionnels et application au dénombrement des relations binaires connexes, C. R. Acad. Sci. Paris Ser. A-B 268 1969 A577-A579.
Index entries for linear recurrences with constant coefficients, signature (-195, 15886, -726290, 20952193, -403792115, 5336718048, -48588590600, 299693200656, -1195947048240, 2785165036416, -2872859996160).

Cf. A001047, A002501, A002502, A005333, A093732.

Table[63^n-6*32^n-15*18^n+30*17^n-10*14^n+120*11^n-120*10^n+30*9^n-270*8^n+360*7^n-120*6^n, {n,1,25}] (* G. C. Greubel, Oct 06 2017 *)
CoefficientList[Series[x (96368590080x^9+27682953984x^8-13185435000x^7+774468980x^6+ 143028190x^5-19071533x^4+626800x^3+6970x^2-470x-1)/((6x-1)(7x-1)(8x-1)(9x-1)(10x-1)(11x-1)(14x-1)(17x-1)(18x-1)(32x-1)(63x-1)),{x,0,20}],x] (* or *) LinearRecurrence[{195,-15886,726290,-20952193,403792115,-5336718048,48588590600,-299693200656,1195947048240,-2785165036416,2872859996160},{0,1,665,106819,10365005,805351531,56294206205,3735873535339,241600284318365,15423235216318411,978180744322139645},20] (* Harvey P. Dale, Sep 23 2023 *)

for(n=1,25, print1(63^n-6*32^n-15*18^n+30*17^n-10*14^n+120*11^n-120*10^n+30*9^n-270*8^n+360*7^n-120*6^n, ", ")) \\ G. C. Greubel, Oct 06 2017

a(n) = 63^n - 6*32^n - 15*18^n + 30*17^n - 10*14^n + 120*11^n - 120*10^n + 30*9^n - 270*8^n + 360*7^n - 120*6^n.

G.f.: x*(96368590080*x^9 + 27682953984*x^8 - 13185435000*x^7 + 774468980*x^6 + 143028190*x^5 - 19071533*x^4 + 626800*x^3 + 6970*x^2 - 470*x - 1) / ((6*x -1)*(7*x -1)*(8*x -1)*(9*x -1)*(10*x -1)*(11*x -1)*(14*x -1)*(17*x -1)*(18*x -1)*(32*x -1)*(63*x -1)). - Colin Barker, Jul 07 2013

A262307 Array read by antidiagonals: T(m,n) = number of m X n binary matrices with all 1's connected and no zero rows or columns.

Original entry on oeis.org

1, 1, 1, 1, 5, 1, 1, 19, 19, 1, 1, 65, 205, 65, 1, 1, 211, 1795, 1795, 211, 1, 1, 665, 14221, 36317, 14221, 665, 1, 1, 2059, 106819, 636331, 636331, 106819, 2059, 1, 1, 6305, 778765, 10365005, 23679901, 10365005, 778765, 6305, 1

Offset: 1

N. J. A. Sloane, Oct 04 2015

Two 1's are connected if they are in the same row or column. The requirement is for them to form a single connected set.
The number of m X n binary matrices with no zero rows or columns is given by A183109(m, n). If there are multiple components (not connected) then they cannot share either rows or columns. For i < n and j < m there are T(i,j) ways of creating an i X j component that occupies the first row. Its remaining i-1 rows may be on any of the remaining m-1 rows with its j columns on any of the n columns. The m-i rows and n-j columns not used by this component can be any matrix with no zero rows or columns.
T(m,n) is also the number of bipartite connected labeled graphs with parts of size m and n. (See A005333, A227322.)
This is the array a(m,n) in Kreweras (1969). Kreweras describes this as a symmetric triangle read by rows, giving numbers of connected relations.
The companion array b(m,n) (and the first few of its diagonals) in Kreweras (1969) should also be added to the OEIS if they are not already present.

			Table starts:
==========================================================================
m\n| 1    2      3         4           5             6               7
---|----------------------------------------------------------------------
1  | 1    1      1         1           1             1               1 ...
2  | 1    5     19        65         211           665            2059 ...
3  | 1   19    205      1795       14221        106819          778765 ...
4  | 1   65   1795     36317      636331      10365005       162470155 ...
5  | 1  211  14221    636331    23679901     805351531     26175881341 ...
6  | 1  665 106819  10365005   805351531   56294206205   3735873535339 ...
7  | 1 2059 778765 162470155 26175881341 3735873535339 502757743028605 ...
...
As a triangle, this begins:
  1;
  1,    1;
  1,    5,      1;
  1,   19,     19,      1;
  1,   65,    205,     65,      1;
  1,  211,   1795,   1795,    211,      1;
  1,  665,  14221,  36317,  14221,    665,    1;
  1, 2059, 106819, 636331, 636331, 106819, 2059, 1;
  ...

Andrew Howroyd, Table of n, a(n) for n = 1..780
G. Kreweras, Inversion des polynômes de Bell bidimensionnels et application au dénombrement des relations binaires connexes, C. R. Acad. Sci. Paris Ser. A-B 268 1969 A577-A579.

Essentially same table as triangle A227322 (where the antidiagonals only go halfway).
Main diagonal is A005333.
Initial diagonals give A001047, A002501, A002502.
Cf. A226658, A123260, A286189, A183109, A048291, A287274.

A183109[n_, m_] := Sum[(-1)^j*Binomial[m, j]*(2^(m-j) - 1)^n, {j, 0, m}];
T[m_, n_] := A183109[m, n] - Sum[T[i, j]*A183109[m - i, n - j] Binomial[m - 1, i - 1]*Binomial[n, j], {i, 1, m - 1}, {j, 1, n - 1}];
Table[T[m - n + 1, n], {m, 1, 9}, {n, 1, m}] // Flatten (* Jean-François Alcover, Oct 08 2017, after Andrew Howroyd *)

G(N)={my(S=matrix(N,N), T=matrix(N,N));
for(m=1,N,for(n=1,N,
S[m,n]=sum(j=0, m, (-1)^j*binomial(m, j)*(2^(m - j) - 1)^n);
T[m,n]=S[m,n]-sum(i=1, m-1, sum(j=1, n-1, T[i,j]*S[m-i,n-j]*binomial(m-1,i-1)*binomial(n,j)));
));T}
G(7) \\ Andrew Howroyd, May 22 2017

T(m,n) = A183109(m,n) - Sum_{i=1..m-1} Sum_{j=1..n-1} T(i,j)*A183109(m-i, n-j)*binomial(m-1,i-1)*binomial(n,j). - Andrew Howroyd, May 22 2017

Revised by N. J. A. Sloane, May 26 2017, to incorporate material from Andrew Howroyd's May 22 2017 submission (formerly A287297), which was essentially identical to this, although giving an alternative description and more information.

A114936 Number of connected (4,n)-hypergraphs (without empty edges).

Original entry on oeis.org

0, 1, 10, 135, 1992, 30166, 458885, 6965225, 105358102, 1588998756, 23915093535, 359444209015, 5397938190512, 81022969645346, 1215801458118985, 18240857019892005, 273644796626023722, 4104936328561231936

Offset: 0

Goran Kilibarda and Vladeta Jovovic, Jan 08 2006

G. C. Greubel, Table of n, a(n) for n = 0..845
Goran Kilibarda and Vladeta Jovovic, Enumeration of some classes of T_0-hypergraphs, arXiv:1411.4187 [math.CO], 2014.

Cf. A002501, A002502, A093732, A093732, A093733, A093734, A114935, A114937.

With[{nmax = 50}, CoefficientList[Series[(1/4!)*(Exp[15*x] - 4*Exp[8*x] + 6*Exp[7*x] - 3*Exp[6*x] + 12*Exp[5*x] - 24*Exp[4*x] + 23*Exp[3*x] - 11*Exp[2*x] + 6*Exp[x] - 6), {x, 0, nmax}], x] Range[0, nmax]!] (* G. C. Greubel, Oct 07 2017 *)

x='x+O('x^50); concat([0], Vec(serlaplace((1/4!)*(exp(15*x) - 4*exp(8*x) + 6*exp(7*x) - 3*exp(6*x) + 12*exp(5*x) - 24*exp(4*x) + 23*exp(3*x) - 11*exp(2*x) + 6*exp(x) - 6)))) \\ G. C. Greubel, Oct 07 2017

E.g.f.: (1/4!)*(exp(15*x) - 4*exp(8*x) + 6*exp(7*x) - 3*exp(6*x) + 12*exp(5*x) - 24*exp(4*x) + 23*exp(3*x) - 11*exp(2*x) + 6*exp(x) - 6).

A114935 Number of connected (3,n)-hypergraphs (without empty edges).

Original entry on oeis.org

0, 1, 6, 44, 332, 2476, 18136, 130824, 933372, 6610676, 46603616, 327603904, 2298933412, 16115938476, 112906938696, 790735321784, 5536710117452, 38763269947876, 271368229299376, 1899679393564464, 13298164198917492

Offset: 0

Goran Kilibarda and Vladeta Jovovic, Jan 08 2006

G. C. Greubel, Table of n, a(n) for n = 0..1000
Goran Kilibarda and Vladeta Jovovic, Enumeration of some classes of T_0-hypergraphs, arXiv:1411.4187 [math.CO], 2014.

Cf. A002501, A002502, A093732, A093732, A093733, A114934, A114936, A114937.

With[{nmax = 50}, CoefficientList[Series[(1/3!)*(Exp[7*x] - 3*Exp[4*x] + 5*Exp[3*x] - 3*Exp[2*x] + 2*Exp[x] - 2), {x, 0, nmax}], x] Range[0, nmax]!] (* G. C. Greubel, Oct 07 2017 *)

x='x+O('x^50); concat([0], Vec(serlaplace((1/3!)*(exp(7*x) -3*exp(4*x) +5*exp(3*x) -3*exp(2*x) +2*exp(x) - 2)))) \\ G. C. Greubel, Oct 07 2017

E.g.f.: (1/3!)*(exp(7*x) -3*exp(4*x) +5*exp(3*x) -3*exp(2*x) +2*exp(x) - 2).

A114937 Number of connected (5,n)-hypergraphs (without empty edges).

Original entry on oeis.org

0, 1, 15, 336, 8880, 254596, 7606446, 231899522, 7137539256, 220623286632, 6831984816402, 211719998195278, 6562887569336652, 203453536535818388, 6307290799931347878, 195532244201392935354, 6061637498660735815968

Offset: 0

Goran Kilibarda and Vladeta Jovovic, Jan 08 2006

Goran Kilibarda and Vladeta Jovovic, Enumeration of some classes of T_0-hypergraphs, arXiv:1411.4187 [math.CO], 2014.

Cf. A002501, A002502, A093732, A093733, A114932-A114936.

E.g.f.: (1/5!)*(exp(31*x) - 5*exp(16*x) + 10*exp(15*x) - 10*exp(10*x) + 20*exp(9*x) - 40*exp(8*x) + 65*exp(7*x) - 90*exp(6*x) + 144*exp(5*x) - 165*exp(4*x) + 120*exp(3*x) - 50*exp(2*x) + 24*exp(x) - 24).

A114934 Number of connected (5,n)-hypergraphs (without empty edges and without multiple edges).

Original entry on oeis.org

0, 0, 0, 21, 2773, 148365, 5878391, 204819447, 6721694469, 214306917321, 6736603947907, 210284186632443, 6541309609120385, 203129541349695597, 6302428271530970943, 195459285517696665759, 6060542952694406463421

Offset: 0

Goran Kilibarda and Vladeta Jovovic, Jan 08 2006

G. C. Greubel, Table of n, a(n) for n = 0..670
Goran Kilibarda and Vladeta Jovovic, Enumeration of some classes of T_0-hypergraphs, arXiv:1411.4187 [math.CO], 2014.

Cf. A002501, A002502, A093732, A093732, A114933, A114935, A114936, A114937.

With[{nmax = 50}, CoefficientList[Series[(1/5!)*(Exp[31*x] - 5*Exp[16*x] - 10*Exp[15*x] - 10*Exp[10*x] + 20*Exp[9*x] + 40*Exp[8*x] + 65*Exp[7*x] - 30*Exp[6*x] - 96*Exp[5*x] - 45*Exp[4*x] + 20*Exp[3*x] + 50*Exp[2*x] + 24*Exp[x] - 24), {x, 0, nmax}], x] Range[0, nmax]!] (* G. C. Greubel, Oct 07 2017 *)

x='x+O('x^50); concat([0,0,0], Vec(serlaplace((1/5!)*(exp(31*x) - 5*exp(16*x) - 10*exp(15*x) - 10*exp(10*x) + 20*exp(9*x) + 40*exp(8*x) + 65*exp(7*x) - 30*exp(6*x) - 96*exp(5*x) - 45*exp(4*x) + 20*exp(3*x) + 50*exp(2*x) + 24*exp(x) - 24)))) \\ G. C. Greubel, Oct 07 2017

E.g.f.: (1/5!)*(exp(31*x) - 5*exp(16*x) - 10*exp(15*x) - 10*exp(10*x) + 20*exp(9*x) + 40*exp(8*x) + 65*exp(7*x) - 30*exp(6*x) - 96*exp(5*x) - 45*exp(4*x) + 20*exp(3*x) + 50*exp(2*x) + 24*exp(x) - 24).

A114933 Number of connected (4,n)-hypergraphs (without empty edges and without multiple edges).

Original entry on oeis.org

0, 0, 0, 32, 1094, 23055, 405475, 6575842, 102567444, 1569195485, 23775369725, 358461659952, 5391042181294, 80974624209115, 1215462744452775, 18238484835400862, 273628186560143144, 4104820038944901945

Offset: 0

Goran Kilibarda and Vladeta Jovovic, Jan 08 2006

G. C. Greubel, Table of n, a(n) for n = 0..845
Goran Kilibarda and Vladeta Jovovic, Enumeration of some classes of T_0-hypergraphs, arXiv:1411.4187 [math.CO], 2014.

Cf. A002501, A002502, A093732, A093732, A114934, A114935, A114936, A114937.

With[{nmax = 50}, CoefficientList[Series[(1/4!)*(Exp[15*x] - 4*Exp[8*x] - 6*Exp[7*x] - 3*Exp[6*x] + 12*Exp[5*x] + 12*Exp[4*x] - Exp[3*x] - 11*Exp[2*x] - 6*Exp[x] + 6), {x, 0, nmax}], x] Range[0, nmax]!] (* G. C. Greubel, Oct 07 2017 *)

x='x+O('x^50); concat([0,0,0], Vec(serlaplace((1/4!)*(exp(15*x)-4*exp(8*x)-6*exp(7*x)-3*exp(6*x)+12*exp(5*x)+12*exp(4*x)-exp(3*x)-11*exp(2*x)-6*exp(x)+6)))) \\ G. C. Greubel, Oct 07 2017

E.g.f.: (1/4!)*(exp(15*x) - 4*exp(8*x) - 6*exp(7*x) - 3*exp(6*x) + 12*exp(5*x) + 12*exp(4*x) - exp(3*x) - 11*exp(2*x) - 6*exp(x) + 6).

A226658 T(n,k)=Number of nXk 0..4 arrays of sums of 2X2 subblocks of some (n+1)X(k+1) binary array.

Original entry on oeis.org

5, 19, 19, 65, 205, 65, 211, 1795, 1795, 211, 665, 14221, 36317, 14221, 665, 2059, 106819, 636331, 636331, 106819, 2059, 6305, 778765, 10365005, 23679901, 10365005, 778765, 6305, 19171, 5581315, 162470155, 805351531, 805351531, 162470155

Offset: 1

R. H. Hardin Jun 14 2013

Table starts
......5.........19...........65............211.............665............2059
.....19........205.........1795..........14221..........106819..........778765
.....65.......1795........36317.........636331........10365005.......162470155
....211......14221.......636331.......23679901.......805351531.....26175881341
....665.....106819.....10365005......805351531.....56294206205...3735873535339
...2059.....778765....162470155....26175881341...3735873535339.502757743028605
...6305....5581315...2495037197...831358677451.241600284318365
..19171...39606541..37898120011.26094426008221
..58025..279447619.572284920845
.175099.1965098125
.527345

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

R. H. Hardin, Table of n, a(n) for n = 1..71

Diagonal is A005333(n+1)
Staircase diagonal is A123281(n-3)
Column 1 is A001047(n+1)
Column 2 is A002501(n+1)
Column 3 is A002502(n+1)
Column 4 is A093732(n+1)
Column 5 is A093733(n+1)

cp's OEIS Frontend

A002501 a(n) = 7^n - 3*4^n + 2*3^n.

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A093732 Number of connected relations.

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A093733 Number of connected relations.

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A262307 Array read by antidiagonals: T(m,n) = number of m X n binary matrices with all 1's connected and no zero rows or columns.

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A114936 Number of connected (4,n)-hypergraphs (without empty edges).

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A114935 Number of connected (3,n)-hypergraphs (without empty edges).

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A114937 Number of connected (5,n)-hypergraphs (without empty edges).

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A114934 Number of connected (5,n)-hypergraphs (without empty edges and without multiple edges).

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A002501 a(n) = 7^n - 34^n + 23^n.