A011971 -id:A011971 - cp's OEIS frontend

A129333 Fourth column of PE^4.

0, 0, 0, 1, 16, 200, 2320, 26460, 303968, 3557904, 42676320, 526076100, 6673368240, 87148818328, 1171554274800, 16206294360620, 230561544221120, 3371256518888480, 50628767109223872, 780358333403627796

Offset: 0

Gottfried Helms, Apr 08 2007

Base matrix is in A011971; second power is in A078937; third power is in A078938; fourth power is in A078939.

Cf. A056857, A078937, A078938, A078944, A078945, A000110.
Cf. A078937, A078938, A129323, A129324, A129325, A027710.
Cf. A129327, A129328, A129329, A078944, A129331, A129332, A129333.

A056857 := proc(n,c) combinat[bell](n-1-c)*binomial(n-1,c) ; end: A078937 := proc(n,c) add( A056857(n,k)*A056857(k+1,c),k=0..n) ; end: A078938 := proc(n,c) add( A078937(n,k)*A056857(k+1,c),k=0..n) ; end: A078939 := proc(n,c) add( A078938(n,k)*A056857(k+1,c),k=0..n) ; end: A129333 := proc(n) A078939(n+1,3) ; end: seq(A129333(n),n=0..25) ; # R. J. Mathar, May 30 2008

A056857[n_, c_] := If[n <= c, 0, BellB[n - 1 - c] Binomial[n - 1, c]];
A078937[n_, c_] := Sum[A056857[n, k] A056857[k + 1, c], {k, 0, n}];
A078938[n_, c_] := Sum[A078937[n, k] A056857[k + 1, c], {k, 0, n}];
A078939[n_, c_] := Sum[A078938[n, k] A056857[k + 1, c], {k, 0, n}];
a[n_] := A078939[n + 1, 3];
a /@ Range[0, 19] (* Jean-François Alcover, Mar 24 2020, after R. J. Mathar *)

PE=exp(matpascal(5))/exp(1); A = PE^4; a(n)= A[ n,4 ] with exact integer arithmetic: PE=exp(matpascal(5)-matid(6)); A = PE^4; a(n)=A[ n,4]

More terms from R. J. Mathar, May 30 2008

A094577 Central Peirce numbers. Number of set partitions of {1,2,..,2n+1} in which n+1 is the smallest of its block.

Original entry on oeis.org

1, 3, 27, 409, 9089, 272947, 10515147, 501178937, 28773452321, 1949230218691, 153281759047387, 13806215066685433, 1408621900803060705, 161278353358629226675, 20555596673435403499083, 2896227959507289559616217, 448371253145121338801335489

Offset: 0

Vladeta Jovovic, May 12 2004

nonn

Let P(n,k) be the number of set partitions of {1,2,..,n} in which k is the smallest of its block. These numbers were introduced by C. S. Peirce (see reference, page 48). If this triangle is displayed as in A123346 (or A011971) then a(n) = A011971(2n, n) are the central Pierce numbers. - Peter Luschny, Jan 18 2011

Named after the American philosopher, logician, mathematician and scientist Charles Sanders Peirce (1839-1914). - Amiram Eldar, Jun 11 2021

			n = 1, S = {1, 2, 3}. k = n+1 = 2. Thus a(1) = card { 13|2, 1|23, 1|2|3 } = 3. - _Peter Luschny_, Jan 18 2011

Donald E. Knuth, The Art of Computer Programming, Vol. 4, Section 7.2.1.5.

Alois P. Heinz, Table of n, a(n) for n = 0..288
Charles Sanders Peirce, On the Algebra of Logic, American Journal of Mathematics, Vol. 3 (1880), pp. 15-57.

Cf. A094574, A020556, A216078.

Main diagonal of array in A011971.

seq(add(binomial(n, k)*(bell(n+k)), k=0..n), n=0..14); # Zerinvary Lajos, Dec 01 2006
# The objective of this implementation is efficiency.
# m -> [a(0), a(1), ..., a(m-1)] for m > 0.
A094577_list := proc(m)
   local A, R, M, n, k, j;
   M := m+m-1; A := array(1..M);
   j := 1; R := 1; A[1] := 1;
   for n from 2 to M do
      A[n] := A[1];
      for k from n by -1 to 2 do
         A[k-1] := A[k-1] + A[k]
      od;
      if is(n,odd) then
         j := j+1; R := R,A[j] fi
   od;
[R] end:
A094577_list(100); # example call - Peter Luschny, Jan 17 2011

f[n_] := Sum[Binomial[n, k]*BellB[2 n - k], {k, 0, n}]; Array[f, 15, 0]

# requires python 3.2 or higher. Otherwise use def'n of accumulate in python docs.
from itertools import accumulate
A094577_list, blist, b = [1], [1], 1
for n in range(2,502):
    blist = list(accumulate([b]+blist))
    b = blist[-1]
    blist = list(accumulate([b]+blist))
    b = blist[-1]
    A094577_list.append(blist[-n])
# Chai Wah Wu, Sep 02 2014, updated Chai Wah Wu, Sep 20 2014

a(n) = Sum_{k=0..n} binomial(n,k)*Bell(2*n-k).
a(n) = Sum_{k=0..n} (-1)^k*binomial(n, k)*Bell(2*n-k+1).
a(n) = exp(-1)*Sum_{k>=0} (k(k+1))^n/k!. - Benoit Cloitre, Dec 30 2005
a(n) = Sum_{k=0..n} binomial(n,k)*Bell(n+k). - Vaclav Kotesovec, Jul 29 2022

A011968 Apply (1+Shift) to Bell numbers.

Original entry on oeis.org

1, 2, 3, 7, 20, 67, 255, 1080, 5017, 25287, 137122, 794545, 4892167, 31858034, 218543759, 1573857867, 11863100692, 93345011951, 764941675963, 6514819011216, 57556900440429, 526593974392123, 4981585554604074, 48658721593531669, 490110875149889635

Offset: 0

N. J. A. Sloane

nonn

Number of set partitions of n+2 with at least one singleton and the smallest element in any singleton is exactly n. The maximum number of singletons is therefore 3. Alternatively, number of set partitions of n+2 with at least one singleton and the largest element in any singleton is exactly 3 (or n+2 if n+2 < 3). For example, a(3)=7 counts the following set partitions of [5]: {1245, 3}, {12, 3, 45}, {124, 3, 5}, {15, 24, 3}, {125, 3, 4}, {14, 25, 3}, {12, 3, 4, 5}. - Olivier Gérard, Oct 29 2007

Let V(N)={v(1),v(2),...,v(N)} denote an ordered set of increasing positive integers containing a pair of adjacent elements that differ by at least 2, that is, v(i),v(i+1) with v(i+1)-v(i) > 1. Then for n > 0, a(n) is the number of partitions of V(n+1) into blocks of nonconsecutive integers. - Augustine O. Munagi, Jul 17 2008

			a(3)=7 because the set {1,3,4,5} has 7 different partitions into blocks of nonconsecutive integers: 14/35, 135/4, 1/35/4, 13/4/5, 14/3/5, 15/3/4, 1/3/4/5.

Olivier Gérard and Karol Penson, A budget of set partitions statistics, in preparation, unpublished as of Sep 22 2011

Chai Wah Wu, Table of n, a(n) for n = 0..500 n = 0..200 from Vincenzo Librandi.
Cohn, Martin; Even, Shimon; Menger, Karl, Jr.; Hooper, Philip K.; On the Number of Partitionings of a Set of n Distinct Objects, Amer. Math. Monthly 69 (1962), no. 8, 782--785. MR1531841.
Cohn, Martin; Even, Shimon; Menger, Karl, Jr.; Hooper, Philip K.; On the Number of Partitionings of a Set of n Distinct Objects, Amer. Math. Monthly 69 (1962), no. 8, 782--785. MR1531841. [Annotated scanned copy]
Augustine O. Munagi, Extended set partitions with successions, European J. Combin. 29(5) (2008), 1298--1308.
Jocelyn Quaintance and Harris Kwong, A combinatorial interpretation of the Catalan and Bell number difference tables, Integers, 13 (2013), #A29.

Cf. A000110, A000296, A011969, A011970.
A diagonal of A011971 and A106436. - N. J. A. Sloane, Jul 31 2012
Cf. A000569, A240936, A321750.

with(combinat): seq(`if`(n>0,bell(n)+bell(n-1),1),n=0..21); # Augustine O. Munagi, Jul 17 2008

# requires python 3.2 or higher. Otherwise use def'n of accumulate in python docs.
from itertools import accumulate
A011968_list, blist, b = [1,2], [1], 1
for _ in range(10**2):
    blist = list(accumulate([b]+blist))
    A011968_list.append(b+blist[-1])
    b = blist[-1] # Chai Wah Wu, Sep 02 2014, updated Chai Wah Wu, Sep 20 2014

For n >= 1, a(n+1) = exp(-1)*Sum_{k>=0} ((k+1)/k!)*k^n. - Benoit Cloitre, Mar 09 2008
For n >= 1, a(n) = Bell(n) + Bell(n-1). - Augustine O. Munagi, Jul 17 2008
G.f.: G(0) where G(k) = 1 - 2*x*(k+1)/((2*k+1)*(2*x*k-1) - x*(2*k+1)*(2*k+3)*(2*x*k-1)/(x*(2*k+3) - 2*(k+1)*(2*x*k+x-1)/G(k+1) )); (recursively defined continued fraction). - Sergei N. Gladkovskii, Dec 19 2012
G.f.: 1 + x*E(0) where E(k) = 1 + 1/(1-x*k-x)/(1-x/(x+1/E(k+1) )); (recursively defined continued fraction). - Sergei N. Gladkovskii, Jan 20 2013
G.f.: 1 + Sum_{k>=0} ( 1+1/(1-x-x*k) )*x^(k+1)/Product_{i=0..k} (1-x*i). - Sergei N. Gladkovskii, Jan 20 2013
a(n) ~ Bell(n) * (1 + LambertW(n)/n). - Vaclav Kotesovec, Jul 28 2021

A011969 Apply (1+Shift)^2 to Bell numbers.

Original entry on oeis.org

1, 3, 5, 10, 27, 87, 322, 1335, 6097, 30304, 162409, 931667, 5686712, 36750201, 250401793, 1792401626, 13436958559, 105208112643, 858286687914, 7279760687179, 64071719451645, 584150874832552, 5508179528996197

Offset: 0

N. J. A. Sloane

nonn

Starting with n=2 (a(2)=5), number of set partitions of n+2 with at least one singleton and the smallest element in any singleton is exactly n-1. The maximum number of singletons is therefore 4. Alternatively, starting with n=2, number of set partitions of n+2 with at least one singleton and the largest element in any singleton is exactly 4. E.g. a(3)=10 counts the following set partitions of [5]: {1345, 2}, {13, 2, 45}, {145, 2, 3}, {134, 2, 5}, {15, 2, 34}, {135, 2, 4}, {14, 2, 35}, {13, 2, 4, 5}, {14, 2, 3, 5}, {15, 2, 3, 4}. - Olivier Gérard, Oct 29 2007

Let V(N)={v(1),v(2),...,v(N)} denote an ordered set of increasing positive integers containing 2 pairs of adjacent elements that differ by at least 2, that is, v(i),v(i+1) with v(i+1)-v(i)>1. Then for n>1, a(n) is the number of partitions of V(n+1) into blocks of nonconsecutive integers. - Augustine O. Munagi, Jul 17 2008

			a(3)=10 because the set {1,3,5,6} has 10 different partitions into blocks of nonconsecutive integers: 15/36, 16/35, 135/6, 136/5, 1/35/6, 1/36/5, 13/5/6, 15/3/6, 16/3/5, 1/3/5/6.

Olivier Gérard and Karol Penson, A budget of set partitions statistics, in preparation, unpublished as of Sep 22 2011

Chai Wah Wu, Table of n, a(n) for n = 0..500 n = 0..200 from Vincenzo Librandi.
Martin Cohn, Shimon Even, Karl Menger, Jr., and Philip K. Hooper, On the Number of Partitionings of a Set of n Distinct Objects, Amer. Math. Monthly 69 (1962), no. 8, 782--785. MR1531841.
Martin Cohn, Shimon Even, Karl Menger, Jr., and Philip K. Hooper, On the Number of Partitionings of a Set of n Distinct Objects, Amer. Math. Monthly 69 (1962), no. 8, 782--785. MR1531841. [Annotated scanned copy]
Augustine O. Munagi, Extended set partitions with successions, European J. Combin. 29(5) (2008), 1298--1308.
Jocelyn Quaintance and Harris Kwong, A combinatorial interpretation of the Catalan and Bell number difference tables, Integers, 13 (2013), #A29.

Cf. A000110, A011968, A011970.

A diagonal of A011971 and A106436. - N. J. A. Sloane, Jul 31 2012

with(combinat): 1,3,seq(`if`(n>1,bell(n)+2*bell(n-1)+bell(n-2),NULL),n=2..22); # Augustine O. Munagi, Jul 17 2008

Join[{1,3},#[[1]]+2#[[2]]+#[[3]]&/@Partition[BellB[Range[0,30]],3,1]] (* Harvey P. Dale, May 05 2023 *)

# requires python 3.2 or higher. Otherwise use def'n of accumulate in python docs.
from itertools import accumulate
A011969_list, blist, b, b2 = [1,3], [1], 1, 1
for _ in range(10**2):
    blist = list(accumulate([b]+blist))
    A011969_list.append(2*b+b2+blist[-1])
    b2, b = b, blist[-1]
# Chai Wah Wu, Sep 02 2014, updated Chai Wah Wu, Sep 20 2014

For n >= 1, a(n+2) = exp(-1)*Sum_{k>=0} (k+1)^2/k!*k^n. - Benoit Cloitre, Mar 09 2008
If n>1, then a(n) = Bell(n) + 2*Bell(n-1) + Bell(n-2). - Augustine O. Munagi, Jul 17 2008
G.f.: -(1+2*x)*(1+x)^2*Sum_{k>=0} x^(2*k)*(4*x*k^2-2*k-2*x-1)/((2*k+1)*(2*x*k-1))*A(k)/B(k) where A(k) = Product_{p=0..k} (2*p+1), B(k) = Product_{p=0..k} (2*p-1)*(2*x*p-x-1)*(2*x*p-2*x-1). - Sergei N. Gladkovskii, Jan 03 2013 [corrected by Jason Yuen, Apr 03 2025]
G.f.: G(0)*(1+x) where G(k) = 1 - 2*x*(k+1)/((2*k+1)*(2*x*k-1) - x*(2*k+1)*(2*k+3)*(2*x*k-1)/(x*(2*k+3) - 2*(k+1)*(2*x*k+x-1)/G(k+1) )); (continued fraction). - Sergei N. Gladkovskii, Jan 03 2013
a(n) ~ Bell(n) * (1 + 2*LambertW(n)/n). - Vaclav Kotesovec, Jul 28 2021

A011970 Apply (1+Shift)^3 to Bell numbers.

Original entry on oeis.org

1, 4, 8, 15, 37, 114, 409, 1657, 7432, 36401, 192713, 1094076, 6618379, 42436913, 287151994, 2042803419, 15229360185, 118645071202, 963494800557, 8138047375093, 71351480138824, 648222594284197, 6092330403828749

Offset: 0

N. J. A. Sloane

nonn

Starting with n=3 (a(3)=15), number of set partitions of n+2 with at least one singleton and the smallest element in any singleton is exactly n-2. The maximum number of singletons is therefore 5. Alternatively, starting with n=3, number of set partitions of n+2 with at least one singleton and the largest element in any singleton is exactly 5. - Olivier Gérard, Oct 29 2007

Let V(N)={v(1),v(2),...,v(N)} denote an ordered set of increasing positive integers containing 3 pairs of adjacent elements that differ by at least 2, that is, v(i),v(i+1) with v(i+1)-v(i)>1. Then for n>2, a(n) is the number of partitions of V(n+1) into blocks of nonconsecutive integers. - Augustine O. Munagi, Jul 17 2008

			a(3)=15 because the set {1,3,5,7} has 15 different partitions which are necessarily into blocks of nonconsecutive integers.

Olivier Gérard and Karol Penson, A budget of set partitions statistics, in preparation, unpublished as of Sep 22 2011

Chai Wah Wu, Table of n, a(n) for n = 0..500
Cohn, Martin; Even, Shimon; Menger, Karl, Jr.; Hooper, Philip K.; On the Number of Partitionings of a Set of n Distinct Objects, Amer. Math. Monthly 69 (1962), no. 8, 782--785. MR1531841.
Cohn, Martin; Even, Shimon; Menger, Karl, Jr.; Hooper, Philip K.; On the Number of Partitionings of a Set of n Distinct Objects, Amer. Math. Monthly 69 (1962), no. 8, 782--785. MR1531841. [Annotated scanned copy]
Augustine O. Munagi, Extended set partitions with successions, European J. Combin. 29(5) (2008), 1298--1308.
Jocelyn Quaintance and Harris Kwong, A combinatorial interpretation of the Catalan and Bell number difference tables, Integers, 13 (2013), #A29.

Cf. A000110.
Cf. A011968, A011969.
A diagonal of A011971 and A106436. - N. J. A. Sloane, Jul 31 2012

with(combinat): 1,4,8,seq(`if`(n>2,bell(n)+3*bell(n-1)+3*bell(n-2)+bell(n-3),NULL),n=3..22); # Augustine O. Munagi, Jul 17 2008

# requires python 3.2 or higher. Otherwise use def'n of accumulate in python docs.
from itertools import accumulate
A011970_list, blist, b, b2, b3 = [1,4,8], [1, 2], 2, 1, 1
for _ in range(498):
    blist = list(accumulate([b]+blist))
    A011970_list.append(3*(b+b2)+b3+blist[-1])
    b3, b2, b = b2, b, blist[-1]
# Chai Wah Wu, Sep 02 2014, updated Chai Wah Wu, Sep 20 2014

If n>2, then bell(n)+3*bell(n-1)+3*bell(n-2)+bell(n-3). - Augustine O. Munagi, Jul 17 2008

A073146 Triangle of numbers {a(n,k), n >= 0, 0 <= k <= n} defined by a(0,0)=1, a(n,0)=A000670(n), a(n,n)=A000629(n), a(n,k) = a(n,k-1) + a(n-1,k-1); a(n+1,0) = Sum_{k=0..n} a(n,k).

Original entry on oeis.org

1, 1, 2, 3, 4, 6, 13, 16, 20, 26, 75, 88, 104, 124, 150, 541, 616, 704, 808, 932, 1082, 4683, 5224, 5840, 6544, 7352, 8284, 9366, 47293, 51976, 57200, 63040, 69584, 76936, 85220, 94586, 545835, 593128, 645104, 702304, 765344, 834928, 911864

Offset: 0

Paul D. Hanna, Jul 18 2002

Related to preferential arrangements of n elements (A000670) and necklaces of sets of labeled beads (A000629).

Row sums are 1, 3, 13, 75, 541, ... (A000670 starting from A000670(1), the second "1"). - Gary W. Adamson, May 31 2005

			Triangle begins:
    1;
    1,   2;
    3,   4,   6;
   13,  16,  20,  26;
   75,  88, 104, 124, 150;
  541, 616, 704, 808, 932, 1082;
  ...

D. Dumont, Matrices d'Euler-Seidel, Sem. Loth. Comb. B05c (1981) 59-78.

Cf. A000670, A000629, A011971.

Main diagonal is in A098696.

Fubini[n_, r_] := Sum[k!*Sum[(-1)^(i+k+r)*(i+r)^(n-r)/(i!*(k-i-r)!), {i, 0, k-r}], {k, r, n}]; Fubini[0, 1] = 1;
a[n_, k_] := Sum[Binomial[k, i-n+k] Fubini[i, 1], {i, n-k, n}];
Table[a[n, k], {n, 0, 8}, {k, 0, n}] // Flatten (* Jean-François Alcover, Mar 30 2016, after Vladeta Jovovic *)

From Vladeta Jovovic, Oct 15 2006: (Start)
Double-exponential generating function: Sum_{n, k} a(n-k, k) x^n/n! y^k/k! = exp(y)/(2-exp(x+y)).
a(n,k) = Sum_{i=n-k..n} binomial(k,i-n+k)*A000670(i). (End)

A108041 Triangle of numbers {a(n,k), n >= 0, 0<=k<=n} defined by a(0,0)=1, a(n,0)=a(n-1,n-1), a(n,k)=a(n,k-1) + Sum_{i=0..k-1} a(n-1,i).

Original entry on oeis.org

1, 1, 2, 2, 3, 7, 7, 9, 19, 42, 42, 49, 100, 210, 443, 443, 485, 977, 2005, 4120, 8473, 8473, 8916, 17874, 36240, 73508, 149131, 302615, 302615, 311088, 622619, 1254196, 2526758, 5090784, 10257191, 20667866, 20667866, 20970481, 41949435, 84210401, 169052379

Offset: 0

N. J. A. Sloane, Jun 01 2005

			1; 1,2; 2,3,7; 7,9,19,42; 42,49,100,210,443; ...

Borders give A108042. Row sums are A108043. Cf. A011971.

f := proc(n,k) local i,t1; option remember; if n=0 and k=0 then 1 elif k=0 then f(n-1,n-1) else add(f(n,i),i=0..k-1) +f(n-1,k-1); fi: end;

A200580 Sum of dimension exponents of supercharacter of unipotent upper triangular matrices.

Original entry on oeis.org

0, 1, 10, 73, 490, 3246, 21814, 150535, 1072786, 7915081, 60512348, 479371384, 3932969516, 33392961185, 293143783762, 2658128519225, 24872012040510, 239916007100054, 2383444110867378, 24363881751014383, 256034413642582418, 2763708806499744097

Offset: 1

Nantel Bergeron, Nov 19 2011

nonn

Supercharacter theory of unipotent upper triangular matrices over a finite field F(2) is indexed by set partitions S(n) of {1,2,..., n} where a set partition P of {1,2,..., n} is a subset { (i,j) : 1 <= i < j <= n}

such that (i,j) in P implies (i,k),(k,j) are not in P for all i

The dimension of the representation associated to the supercharacter indexed by P is given by 2^Dim(P) where Dim(P) = sum [ j-i , (i,j) in P ].

The sequence we have is a(n) = sum [ Dim(P) , P in S(n) ].

Vincenzo Librandi, Table of n, a(n) for n = 1..200
M. Aguiar, C. Andre, C. Benedetti, N. Bergeron, Z. Chen, P. Diaconis, A. Hendrickson, S. Hsiao, I.M. Isaacs, A. Jedwab, K. Johnson, G. Karaali, A. Lauve, T. Le, S. Lewis, H. Li, K. Magaard, E. Marberg, J-C. Novelli, A. Pang, F. Saliola, L. Tevlin, J-Y. Thibon, N. Thiem, V. Venkateswaran, C.R. Vinroot, N. Yan and M. Zabrocki, Supercharacters, symmetric functions in noncommuting variables, and related Hopf algebras, arXiv:1009.4134 [math.CO], 2010-2011.
C. André, Basic characters of the unitriangular group, Journal of Algebra, 175 (1995), 287-319.
B. Chern, P. Diaconis, D. M. Kane and R. C. Rhoades, Closed expressions for averages of set partition statistics, 2013.
Mikhail Khovanov, Victor Ostrik and Yakov Kononov, Two-dimensional topological theories, rational functions and their tensor envelopes, arXiv:2011.14758 [math.QA], 2020.

Cf. A011971 (sequence is computed from the Aitken's array b(n,k)
  a(n) = sum [ k*(n-k)*b(n,k), k=1..n-1 ]).
Cf. A200660, A200673 (other statistics related to supercharacter theory).
Cf. A000110, A226507.

[-2*Bell(n+3)+(n+5)*Bell(n+2): n in [1..30]]; // Vincenzo Librandi, Jul 16 2013

b:=proc(n,k) option remember;
  if n=1 and k=1 then RETURN(1) fi;
  if k=1 then RETURN(b(n-1,n-1)) fi;
  b(n,k-1)+b(n-1,k-1)
end:
a:=proc(n) local res,k;
  res:=0;
  for k to n-1 do res:=res+k*(n-k)*b(n,k) od;
  res
end:
seq(a(n),n=1..34);

Table[-2 BellB[n+3] + (n+5) BellB[n+2], {n, 1, 30}] (* Vincenzo Librandi, Jul 16 2013 *)

a(n) = -2*B(n+2) + (n+4)*B(n+1) where B(i) = Bell numbers A000110. [Chern et al.] - N. J. A. Sloane, Jun 10 2013 [for offset 2]

a(n) ~ n^3 * Bell(n) / LambertW(n)^2 * (1 - 2/LambertW(n)). - Vaclav Kotesovec, Jul 28 2021

A200660 Sum of the number of arcs describing the set partitions of {1,2,...,n}.

Original entry on oeis.org

0, 1, 8, 49, 284, 1658, 9974, 62375, 406832, 2769493, 19668054, 145559632, 1121153604, 8974604065, 74553168520, 641808575961, 5718014325296, 52653303354906, 500515404889978, 4905937052293759, 49530189989912312, 514541524981377909, 5494885265473192914

Offset: 1

Nantel Bergeron, Nov 20 2011

nonn

Supercharacter theory of unipotent upper triangular matrices over a finite field F(2) is indexed by set partitions S(n) of {1,2,...,n} where a set partition P of {1,2,...,n} is a subset { (i,j) : 1 <= i < j <= n} such that (i,j) in P implies (i,k),(k,j) are not in P for all i < l < j.
One of the statistics used to compute the supercharacter table is the number of arcs in P (that is, the cardinality |P| of P).
The sequence we have is arcs(n) = Sum_{P in S(n)} |P|.

Seiichi Manyama, Table of n, a(n) for n = 1..500
M. Aguiar, C. Andre, C. Benedetti, N. Bergeron, Z. Chen, P. Diaconis, A. Hendrickson, S. Hsiao, I. M. Isaacs, A. Jedwab, K. Johnson, G. Karaali, A. Lauve, T. Le, S. Lewis, H. Li, K. Magaard, E. Marberg, J-C. Novelli, A. Pang, F. Saliola, L. Tevlin, J-Y. Thibon, N. Thiem, V. Venkateswaran, C. R. Vinroot, N. Yan, and M. Zabrocki, Supercharacters, symmetric functions in noncommuting variables, and related Hopf algebras, arXiv:1009.4134 [math.CO], 2010-2011.
C. André, Basic characters of the unitriangular group, Journal of Algebra, 175 (1995), 287-319.

Cf. A011971 (sequence is computed from Aitken's array b(n,k) arcs(n) = Sum_{k=1..n-1} k*b(n,k)).
Cf. A200580, A200673 (other statistics related to supercharacter table).
Cf. A367955.

b:=proc(n,k) option remember;
  if n=1 and k=1 then RETURN(1) fi;
  if k=1 then RETURN(b(n-1,n-1)) fi;
  b(n,k-1)+b(n-1,k-1)
end:
arcs:=proc(n) local res,k;
  res:=0;
  for k to n-1 do res:=res+ k*b(n,k) od;
  res
end:
seq(arcs(n),n=1..34);

b[n_, k_] := b[n, k] = Which[n == 1 && k == 1, 1, k == 1, b[n - 1, n - 1], True, b[n, k - 1] + b[n - 1, k - 1]];
arcs[n_] := Module[{res = 0, k}, For[k = 1, k <= n-1, k++, res = res + k * b[n, k]]; res];
Array[arcs, 34] (* Jean-François Alcover, Nov 25 2017, translated from Maple *)

a(n) = Sum_{k=1..n} Stirling2(n,k) * k * (n-k). - Ilya Gutkovskiy, Apr 06 2021

a(n) = Sum_{k=n..n*(n+1)/2} (k-n) * A367955(n,k). - Alois P. Heinz, Dec 11 2023

A298804 Triangle T(n,k) (1 <= k <= n) read by rows: A046936 with rows reversed and offset changed to 1.

Original entry on oeis.org

0, 1, 1, 3, 2, 1, 9, 6, 4, 3, 31, 22, 16, 12, 9, 121, 90, 68, 52, 40, 31, 523, 402, 312, 244, 192, 152, 121

Offset: 1

N. J. A. Sloane, Jan 30 2018, following a suggestion from Don Knuth, Jan 29 2018

This is another version of Moser's version (A046936) of Aitken's array (A011971).
Although offset 0 is better for A011971 and A046936, for this version offset 1 is more appropriate.
Comments from Don Knuth, Jan 29 2018 (Start):
a(n,k) is the number of set partitions (i.e. equivalence classes) in which (i) 1 is not equivalent to 2, ..., nor k; and (ii) the last part, when parts are ordered by their smallest element, has size 1; (iii) that last part isn't simply "1". (Equivalently, n>1.)
It's not difficult to prove this characterization of a(k,n). For example, if we know that there are 22 partitions of {1,2,3,4,5} with 1 inequivalent to 2, and 6 partitions of {1,2,3,4} with
1 inequivalent to 2, then there are 6 partitions of {1,2,3,4,5} with 1 inequivalent to 2 and 1 equivalent to 3. Hence there are 16 with 1 equivalent to neither 2 nor 3.
The same property, but leaving out conditions (ii) and (iii), characterizes Pierce's triangular array A123346.  (End)

			Triangle begins:
0,
1, 1,
3, 2, 1,
9, 6, 4, 3,
31, 22, 16, 12, 9,
121, 90, 68, 52, 40, 31
523, 402, 312, 244, 192, 152, 121
...

Don Knuth, Email to N. J. A. Sloane, Jan 29 2018

Cf. A011971, A040027, A046936, A123346.

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A129333 Fourth column of PE^4.

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A011968 Apply (1+Shift) to Bell numbers.

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A011969 Apply (1+Shift)^2 to Bell numbers.

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A011970 Apply (1+Shift)^3 to Bell numbers.

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A073146 Triangle of numbers {a(n,k), n >= 0, 0 <= k <= n} defined by a(0,0)=1, a(n,0)=A000670(n), a(n,n)=A000629(n), a(n,k) = a(n,k-1) + a(n-1,k-1); a(n+1,0) = Sum_{k=0..n} a(n,k).

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A108041 Triangle of numbers {a(n,k), n >= 0, 0<=k<=n} defined by a(0,0)=1, a(n,0)=a(n-1,n-1), a(n,k)=a(n,k-1) + Sum_{i=0..k-1} a(n-1,i).

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