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 1-9 of 9 results.

A051168 Triangular array T(h,k) for 0 <= k <= h read by rows: T(h,k) = number of binary Lyndon words with k ones and h-k zeros.

Original entry on oeis.org

1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 1, 2, 2, 1, 0, 0, 1, 2, 3, 2, 1, 0, 0, 1, 3, 5, 5, 3, 1, 0, 0, 1, 3, 7, 8, 7, 3, 1, 0, 0, 1, 4, 9, 14, 14, 9, 4, 1, 0, 0, 1, 4, 12, 20, 25, 20, 12, 4, 1, 0, 0, 1, 5, 15, 30, 42, 42, 30, 15, 5, 1, 0, 0, 1, 5, 18, 40, 66, 75, 66, 40, 18, 5, 1, 0, 0, 1, 6
Offset: 0

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Author

Keywords

Comments

T(h,k) is the number of classes of aperiodic binary words of k ones and h-k zeros; words u,v are in the same class if v is a cyclic permutation of u (e.g., u=111000, v=110001) and a word is aperiodic if not a juxtaposition of 2 or more identical subwords.
T(2n, n), T(2n+1, n), T(n, 3) match A022553, A000108, A001840, respectively. Row sums match A001037.
From R. J. Mathar, Jul 31 2008: (Start)
This triangle may also be regarded as the square array A(r,n), the n-th term of the r-th Witt transform of the all-1 sequence, r >= 1, n >= 0, read by antidiagonals:
This array begins as follows:
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9
0 1 2 3 5 7 9 12 15 18 22 26 30 35 40 45 51 57 63
0 1 2 5 8 14 20 30 40 55 70 91 112 140 168 204 240 285 330
0 1 3 7 14 25 42 66 99 143 200 273 364 476 612 775 969 1197 1463
0 1 3 9 20 42 75 132 212 333 497 728 1026 1428 1932 2583 3384 4389 5598
0 1 4 12 30 66 132 245 429 715 1144 1768 2652 3876 5537 7752 10659 14421 19228
0 1 4 15 40 99 212 429 800 1430 2424 3978 6288 9690 14520 21318 30624 43263 60060
0 1 5 18 55 143 333 715 1430 2700 4862 8398 13995 22610 35530 54477 81719 120175
0 1 5 22 70 200 497 1144 2424 4862 9225 16796 29372 49742 81686 130750 204248
0 1 6 26 91 273 728 1768 3978 8398 16796 32065 58786 104006 178296 297160 482885
0 1 6 30 112 364 1026 2652 6288 13995 29372 58786 112632 208012 371384 643842
0 1 7 35 140 476 1428 3876 9690 22610 49742 104006 208012 400023 742900 1337220
0 1 7 40 168 612 1932 5537 14520 35530 81686 178296 371384 742900 1432613 2674440
...
It is essentially symmetric: A(r,r+i) = A(r,r-i+1).
Some of the diagonals are:
A(r,r+1): A000108
A(r,r): A022553
A(r,r-1): A000108
A(r,r+2): A000150
A(r,r+3): A050181
A(r,r+4): A050182
A(r,r+5): A050183
A(r,r-2): A000150 (End)
Fredman (1975) proved that the number S(n, k, v) of vectors (a_0, ..., a_{n-1}) of nonnegative integer components that satisfy a_0 + ... + a_{n-1} = k and Sum_{i=0..n-1} i*a_i = v (mod n) is given by S(n, k, v) = (1/(n + k)) * Sum_{d | gcd(n, k)} A054533(d, v) * binomial((n + k)/d, k/d) = S(k, n, v). This was also proved by Elashvili et al. (1999), who also proved that S(n, k, v) = Sum_{d | gcd(n, k, v)} S(n/d, k/d, 1). Here, S(n, k, 1) = T(n + k, k). - Petros Hadjicostas, Jul 09 2019

Examples

			Triangle begins with:
h=0: 1
h=1: 1, 1
h=2: 0, 1, 0
h=3: 0, 1, 1, 0
h=4: 0, 1, 1, 1,  0
h=5: 0, 1, 2, 2,  1,  0
h=6: 0, 1, 2, 3,  2,  1, 0
h=7: 0, 1, 3, 5,  5,  3, 1, 0
h=8: 0, 1, 3, 7,  8,  7, 3, 1, 0
h=9: 0, 1, 4, 9, 14, 14, 9, 4, 1, 0
...
T(6,3) counts classes {111000},{110100},{110010}, each of 6 aperiodic. The class {100100} contains 3 periodic words, counted by T(3,1) as {100}, consisting of 3 aperiodic words 100,010,001.
		

Crossrefs

Columns 1-11: A000012, A004526(n-1), A001840(n-4), A006918(n-4), A011795(n-1), A011796(n-6), A011797(n-1), A031164(n-9), A011845, A032168, A032169. See also A000150.

Programs

  • Maple
    A := proc(r,n) local gf,d,genf; genf := 1/(1-x) ; gf := 0 ; for d in numtheory[divisors](r) do gf := gf + numtheory[mobius](d)*(subs(x= x^d,genf))^(r/d) ; od: gf := expand(gf/r) ; coeftayl(gf,x=0,n) ; end proc:
    A051168 := proc(n,k) if n<=1 then 1; elif n=0 or n=k then 0; else A(n-k,k) ; end if;
    end proc:
    seq(seq(A051168(n,k),k=0..n),n=0..10) ; # R. J. Mathar, Mar 29 2011
  • Mathematica
    Table[If[n===0,1,1/n Plus@@(MoebiusMu[ # ]Binomial[n/#,k/# ]&/@ Divisors[GCD[n,k]])],{n,0,12},{k,0,n}] (* Wouter Meeussen, Jul 20 2008 *)
  • PARI
    {T(n, k) = local(A, ps, c); if( k<0 || k>n, 0, if( n==0 && k==0, 1, A = x * O(x^n) + y * O(y^n); ps = 1 - x - y + A; for( m=1, n, for( i=0, m, c = polcoeff( polcoeff(ps, i, x), m-i, y); if( m==n && i==k, break(2), ps *= (1 -y^(m-i) * x^i + A)^c))); -c))} /* Michael Somos, Jul 03 2004 */
    
  • PARI
    T(n,k) = if (n==0, 1, (1/n) * sumdiv(gcd(n,k), d, moebius(d) * binomial(n/d,k/d)));
    tabl(nn) = for (n=0, nn, for (k=0, n, print1(T(n, k), ", ")); print); \\ Michel Marcus, May 16 2018

Formula

T(h, k) = 1 for (h, k) in {(0, 0), (1, 0), (1, 1)}; T(h, k) = 0 if h >= 2 and k = 0 or k = h. Otherwise, T(h, k) = (1/h)*(C(h, k)-S(h, k)), where S(h, k) = Sum_{d <= 2, d|h, d|k} (h/d)*T(h/d, k/d).
1 - x - y = Product_{i,j} (1 - x^i * y^j)^T(i+j, j) where i >= 0, j >= 0 are not both zero. - Michael Somos, Jul 03 2004
The prime rows are given by (1+x)^p/p with noninteger coefficients rounded to zero. E.g., for h = 2 below, (1 + x)^2/2 = (1 + 2*x + x^2)/2 = 0.5 + x + 0.5*x^2 gives (0,1,0). - Tom Copeland, Oct 21 2014
T(n,k) = (1/n) * Sum_{d | gcd(n,k)} mu(d) * binomial(n/d, k/d), for n > 0. - Andrew Howroyd, Mar 26 2017
From Petros Hadjicostas, Jun 16 2019: (Start)
O.g.f. for column k >= 1: (x^k/k) * Sum_{d|k} mu(d)/(1 - x^d)^(k/d).
Bivariate o.g.f.: Sum_{n,k >= 0} T(n, k)*x^n*y^k = 1 - Sum_{d >= 1} (mu(d)/d) *log(1 - x^d * (1 + y^d)).
(End)

A245558 Square array read by antidiagonals: T(n,k) = number of n-tuples of nonnegative integers (u_0,...,u_{n-1}) satisfying Sum_{j=0..n-1} j*u_j == 1 mod n and Sum_{j=0..n-1} u_j = m.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 2, 3, 2, 1, 1, 3, 5, 5, 3, 1, 1, 3, 7, 8, 7, 3, 1, 1, 4, 9, 14, 14, 9, 4, 1, 1, 4, 12, 20, 25, 20, 12, 4, 1, 1, 5, 15, 30, 42, 42, 30, 15, 5, 1, 1, 5, 18, 40, 66, 75, 66, 40, 18, 5, 1, 1, 6, 22, 55, 99, 132, 132, 99, 55, 22, 6, 1
Offset: 1

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Author

N. J. A. Sloane, Aug 07 2014

Keywords

Comments

The array is symmetric; for the entries on or below the diagonal see A245559.
If the congruence in the definition is changed from Sum_{j=0..n-1} j*u_j == 1 mod n to Sum_{j=0..n-1} j*u_j == 0 mod n we get the array shown in A241926, A047996, and A037306.
Differs from A011847 from row n = 9, k = 4 on; if the rows are surrounded by 0's, this yields A051168 without its rows 0 and 1, i.e., a(1) is A051168(2,1). - M. F. Hasler, Sep 29 2018
This array was first studied by Fredman (1975). - Petros Hadjicostas, Jul 10 2019

Examples

			Square array begins:
  1, 1,  1,  1,   1,   1,    1,    1,    1,    1, ...
  1, 1,  2,  2,   3,   3,    4,    4,    5,    5, ...
  1, 2,  3,  5,   7,   9,   12,   15,   18,   22, ...
  1, 2,  5,  8,  14,  20,   30,   40,   55,   70, ...
  1, 3,  7, 14,  25,  42,   66,   99,  143,  200, ...
  1, 3,  9, 20,  42,  75,  132,  212,  333,  497, ...
  1, 4, 12, 30,  66, 132,  245,  429,  715, 1144, ...
  1, 4, 15, 40,  99, 212,  429,  800, 1430, 2424, ...
  1, 5, 18, 55, 143, 333,  715, 1430, 2700, 4862, ...
  1, 5, 22, 70, 200, 497, 1144, 2424, 4862, 9225, ...
  ...
Reading by antidiagonals, we get:
  1;
  1, 1;
  1, 1,  1;
  1, 2,  2,  1;
  1, 2,  3,  2,  1;
  1, 3,  5,  5,  3,   1;
  1, 3,  7,  8,  7,   3,   1;
  1, 4,  9, 14, 14,   9,   4,  1;
  1, 4, 12, 20, 25,  20,  12,  4,  1;
  1, 5, 15, 30, 42,  42,  30, 15,  5,  1;
  1, 5, 18, 40, 66,  75,  66, 40, 18,  5, 1;
  1, 6, 22, 55, 99, 132, 132, 99, 55, 22, 6, 1;
  ...
		

Crossrefs

This array is very similar to but different from A011847.
Rows include A001840, A006918, A051170, A011796, A011797, A031164. Main diagonal is A022553.

Programs

  • Maple
    # To produce the first 10 rows and columns (as on page 174 of the Elashvili et al. 1999 reference):
    with(numtheory):
    cnk:=(n,k) -> add(mobius(n/d)*d, d in divisors(gcd(n,k)));
    anmk:=(n,m,k)->(1/(n+m))*add( cnk(d,k)*binomial((n+m)/d,n/d), d in divisors(gcd(n,m))); # anmk(n,m,k) is the value of a_k(n,m) as in Theorem 1, Equation (4), of the Elashvili et al. 1999 reference.
    r2:=(n,k)->[seq(anmk(n,m,k),m=1..10)];
    for n from 1 to 10 do lprint(r2(n,1)); od:
  • Mathematica
    rows = 12;
    cnk[n_, k_] := Sum[MoebiusMu[n/d] d, {d , Divisors[GCD[n, k]]}];
    anmk[n_, m_, k_] := (1/(n+m)) Sum[cnk[d, k] Binomial[(n+m)/d, n/d], {d, Divisors[GCD[n, m]]}];
    r2[n_, k_] := Table[anmk[n, m, k], {m, 1, rows}];
    T = Table[r2[n, 1], {n, 1, rows}];
    Table[T[[n-k+1, k]], {n, 1, rows}, {k, 1, n}] // Flatten (* Jean-François Alcover, Nov 05 2018, from Maple *)

A381289 Number of subsets of 6 integers between 1 and n such that their sum is 0 modulo n.

Original entry on oeis.org

1, 3, 10, 20, 42, 76, 132, 212, 335, 497, 728, 1028, 1428, 1932, 2586, 3384, 4389, 5601, 7084, 8844, 10966, 13442, 16380, 19780, 23751, 28301, 33566, 39536, 46376, 54086, 62832, 72624, 83661, 95931, 109668, 124872, 141778, 160398, 181006
Offset: 7

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Author

Keywords

Comments

For an integer s multiple of 6, this is also the number of subsets of 6 integers between 1 and n such that their sum is s modulo n.

Examples

			For n=8, there are a(8)=3 order 6 subsets of Z/8Z with sum equal to 0 mod 8.
		

Crossrefs

Cf. A011796.

Formula

G.f.: x^7*(1 + x + 3*x^2 + 2*x^4 + 4*x^5 + x^6 - x^7 + x^8)/((1 - x)^2*(1 - x^2)^2*(1 - x^3)*(1 - x^6)). - David Broadhurst, Feb 19 2025

A381290 Number of subsets of 6 integers between 1 and n such that their sum is 1 modulo n.

Original entry on oeis.org

1, 4, 9, 22, 42, 78, 132, 217, 333, 504, 728, 1035, 1428, 1944, 2583, 3399, 4389, 5616, 7084, 8866, 10962, 13468, 16380, 19806, 23751, 28336, 33561, 39576, 46376, 54126, 62832, 72675, 83655, 95988, 109668, 124929, 141778, 160468, 180999
Offset: 7

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Author

Keywords

Comments

For s an integer such that GCD(s,6)=1, this is also the number of subsets of 6 integers between 1 and n such that their sum is s modulo n.

Examples

			For n=7, a(7)=1 since the set {0,1,2,3,4,5} is the unique order 6 subset of Z/7Z with sum equal to 1 mod 7.
		

Crossrefs

Formula

G.f.: x^7*(1 + 2*x + 3*x^3 + 2*x^4 + 2*x^5 + x^6 + x^7)/((1 - x)^2*(1 - x^2)^2*(1 - x^3)*(1 - x^6)).

A381291 Number of subsets of 8 integers between 1 and n such that their sum is 0 modulo n.

Original entry on oeis.org

1, 5, 15, 43, 99, 217, 429, 809, 1430, 2438, 3978, 6310, 9690, 14550, 21318, 30666, 43263, 60115, 82225, 111041, 148005, 195143, 254475, 328755, 420732, 534076, 672452, 840652, 1043460, 1287036, 1577532, 1922740, 2330445, 2810385, 3372291, 4028183, 4790071
Offset: 9

Views

Author

Keywords

Comments

For an integer s multiple of 8, this is also the number of subsets of 8 integers between 1 and n such that their sum is s modulo n.

Examples

			For n=10, there are a(10)=5 order 8 subsets of Z/10Z with sum equal to 0 mod 10.
		

Crossrefs

Formula

G.f.: x^9*(1 + x - x^2 + 7*x^3 - 4*x^4 + 6*x^5 + 4*x^6 - 4*x^7 + 3*x^8 + 5*x^9 - 3*x^10 + x^11)/((1 - x)^4*(1 - x^2)^2*(1 - x^4)*(1 - x^8)).

A263318 Number of aperiodic necklaces (Lyndon words) with 9 black beads and n white beads.

Original entry on oeis.org

0, 1, 5, 18, 55, 143, 333, 715, 1430, 2700, 4862, 8398, 13995, 22610, 35530, 54477, 81719, 120175, 173583, 246675, 345345, 476901, 650325, 876525, 1168695, 1542684, 2017356, 2615085, 3362260, 4289780, 5433714, 6835972, 8544965, 10616463, 13114465, 16112057
Offset: 0

Views

Author

Criel Merino, Pedro Antonio, Oct 14 2015

Keywords

Comments

A row of triangle A051168.

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[(x (x^4 - x^3 + 3*x^2 - x + 1))/((x^2 + x + 1)^3 (1 - x)^9), {x, 0, 40}], x] (* Wesley Ivan Hurt, Oct 15 2015 *)
    CoefficientList[Series[((-1+x^3)^-3-(-1+x)^-9)/9,{x,0,40}],x] (* Herbert Kociemba, Oct 16 2016 *)
    LinearRecurrence[{6,-15,23,-33,51,-64,63,-63,64,-51,33,-23,15,-6,1},{0,1,5,18,55,143,333,715,1430,2700,4862,8398,13995,22610,35530},40] (* Harvey P. Dale, Feb 10 2023 *)
  • PARI
    a(n)= (1/(n+9))*sumdiv(gcd(n+9,9), d, moebius(d)*binomial( (n+9)/d , 9/d )); \\ Michel Marcus, Oct 14 2015
    
  • Python
    from sympy import mobius, binomial, gcd, divisors
    print([sum(mobius(d) * binomial((n + 9)//d, 9//d) for d in divisors(gcd(n + 9, 9))) // (n + 9) for n in range(51)]) # Indranil Ghosh, Mar 26 2017

Formula

a(n) = (1/(n+9))*Sum_{d divides gcd(n+9,9)} mu(d)*binomial((n+9)/d, 9/d).
G.f.: (x*(x^4-x^3+3*x^2-x+1))/((x^2+x+1)^3*(1-x)^9).
G.f.: ((-1+x^3)^-3-(-1+x)^-9)/9. - Herbert Kociemba, Oct 16 2016

Extensions

More terms from Michel Marcus, Oct 14 2015

A381350 Number of subsets of 8 integers between 1 and n such that their sum is 2 modulo n.

Original entry on oeis.org

1, 5, 15, 42, 99, 217, 429, 808, 1430, 2438, 3978, 6308, 9690, 14550, 21318, 30664, 43263, 60115, 82225, 111038, 148005, 195143, 254475, 328752, 420732, 534076, 672452, 840648, 1043460, 1287036, 1577532, 1922736, 2330445, 2810385, 3372291, 4028178, 4790071, 5672645
Offset: 9

Views

Author

Xavier Roulleau, Feb 21 2025

Keywords

Comments

For s an integer such that GCD(s,8)=2, this is also the number of subsets of 8 integers between 1 and n such that their sum is s modulo n.

Examples

			For n=10, there are a(10)=5 order 8 subsets of Z/10Z with sum equal to 2 mod 10.
		

Crossrefs

Formula

G.f.: x^9*(1 + x - x^2 + 6*x^3 + 2*x^5 + 6*x^7 - x^8 + x^9 + x^10)/((1 - x)^4*(1 - x^2)^2*(1 - x^4)*(1 - x^8)).
a(n) = (n - 4)*(2520 - 24*(281 + 35*(-1)^n)*n + 5*(1039 + 21*(-1)^n)*n^2 - 2112*n^3 + 452*n^4 - 48*n^5 + 2*n^6 - 2520*A056594(n))/80640. - Stefano Spezia, Feb 21 2025

A050191 T(n,6), array T as in A050186; a count of aperiodic binary words.

Original entry on oeis.org

0, 7, 24, 81, 200, 462, 900, 1716, 2968, 4995, 7952, 12376, 18468, 27132, 38640, 54243, 74448, 100947, 134352, 177100, 229944, 295974, 376376, 475020, 593280, 736281, 905632, 1107513, 1344224, 1623160, 1946916
Offset: 6

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Author

Keywords

Crossrefs

Formula

Seems to be n*A011796.

A381351 Number of subsets of 9 integers between 1 and n such that their sum is 3 modulo n.

Original entry on oeis.org

1, 5, 19, 55, 143, 335, 715, 1430, 2703, 4862, 8398, 14000, 22610, 35530, 54484, 81719, 120175, 173592, 246675, 345345, 476913, 650325, 876525, 1168710, 1542684, 2017356, 2615103, 3362260, 4289780, 5433736, 6835972, 8544965, 10616489, 13114465
Offset: 10

Views

Author

Xavier Roulleau, Feb 21 2025

Keywords

Comments

For s an integer such that GCD(s,9)=3, this is also the number of subsets of 9 integers between 1 and n such that their sum is s modulo n.

Examples

			For n=10, there are a(10)=1 order 9 subsets of Z/10Z with sum equal to 3 mod 10.
		

Crossrefs

Formula

G.f.: x^10*(1 - x + 4*x^2 - 6*x^3 + 15*x^4 - 17*x^5 + 15*x^6 - 6*x^7 + 4*x^8 - x^9 + x^10)/((1 - x)^6*(1 - x^3)^2*(1 - x^9)).
Showing 1-9 of 9 results.