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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A203469 a(n) = v(n)/A000178(n), v = A093883 and A000178 = (superfactorials).

Original entry on oeis.org

1, 3, 30, 1050, 132300, 61122600, 104886381600, 674943865596000, 16407885372638760000, 1515727634953623371280000, 534621388490302221024396480000, 722849817707190846398223943885440000, 3759035907022704558524683975387453632000000
Offset: 1

Views

Author

Clark Kimberling, Jan 02 2012

Keywords

Crossrefs

Programs

  • Magma
    [(&*[Binomial(2*n-k,k): k in [1..n]]): n in [1..20]]; // G. C. Greubel, Aug 29 2023
    
  • Mathematica
    (* First program *)
    f[j_]:= j; z = 16;
    v[n_]:= Product[Product[f[k] + f[j], {j,k-1}], {k,2,n}]
    d[n_]:= Product[(i-1)!, {i,n}]
    Table[v[n], {n,z}]           (* A093883 *)
    Table[v[n+1]/v[n], {n,z-1}]  (* A006963 *)
    Table[v[n]/d[n], {n,20}]     (* A203469 *)
    (* Second program *)
    Table[Product[Binomial[2*n-j,j], {j,n}], {n,20}] (* G. C. Greubel, Aug 29 2023 *)
  • SageMath
    [product(binomial(2*n-j,j) for j in range(n)) for n in range(1, 20)] # G. C. Greubel, Aug 29 2023

Formula

a(n) = Product_{i=1..n} binomial(2n-i,i). - Enrique Pérez Herrero, Feb 20 2013
From G. C. Greubel, Aug 29 2023: (Start)
a(n) = (2^n/sqrt(Pi))^n*BarnesG(n+3/2)/(BarnesG(n+2)*BarnesG(3/2)).
a(n) = (n!/2^(n-1))*Product_{j=1..n-1} Catalan(j). (End)
a(n) ~ A^(3/2) * exp(n/2 - 1/8) * 2^(n^2 - 7/24) / (Pi^(n/2 + 1/2) * n^(n/2 + 3/8)), where A is the Glaisher-Kinkelin constant A074962. - Vaclav Kotesovec, Nov 26 2023

A218566 Triangle T[r,c]=(r-1)*binomial(r-1,c-1)*(c-1)!*A093883(c), read by rows.

Original entry on oeis.org

0, 1, 3, 2, 12, 240, 3, 27, 1080, 226800, 4, 48, 2880, 1209600, 3657830400, 5, 75, 6000, 3780000, 22861440000, 1267438233600000, 6, 108, 10800, 9072000, 82301184000, 9125555281920000, 11274806061917798400000
Offset: 1

Views

Author

M. F. Hasler, Nov 02 2012

Keywords

Comments

T[b,d] gives the number of positive numbers that can be written in base b with d(d+1)/2 digits such that for each k=1,...,d some digit appears exactly k times, cf. A218560, A167819, A218556 and related sequences.

Examples

			The first 6 rows of the triangle are:
r=1: 0;
r=2: 1, 3;
r=3: 2, 12,  240;
r=4: 3, 27,  1080,  226800;
r=5: 4, 48,  2880,  1209600,  3657830400;
r=6: 5, 75,  6000,  3780000,  22861440000,  1267438233600000.
Row 2 counts the numbers 1 and 4=100[2], 5=101[2], 6=110[2].
Row 3 counts the numbers {1, 2} and {9=100[3], 10=101[3], 12=110[3], 14=112[3], 16=121[3], ..., 25=221[3]} and {248=100012[3], ..., 714=222110[3]}.
		

Programs

  • PARI
    T(r,c)=(r-1)*binomial(r-1,c-1)*(c-1)!*A093883(c)

Formula

T[r,1] = r-1. T[r,2] = 3(r-1)^2. T[r,3] = 60(r-2)(r-1)^2, etc.

A006963 Number of planar embedded labeled trees with n nodes: (2*n-3)!/(n-1)! for n >= 2, a(1) = 1.

Original entry on oeis.org

1, 1, 3, 20, 210, 3024, 55440, 1235520, 32432400, 980179200, 33522128640, 1279935820800, 53970627110400, 2490952020480000, 124903451312640000, 6761440164390912000, 393008709555221760000, 24412776311194951680000, 1613955767240110694400000
Offset: 1

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Author

Keywords

Comments

For n>1: central terms of the triangle in A173333; cf. A001761, A001813. - Reinhard Zumkeller, Feb 19 2010
Can be obtained from the Vandermonde permanent of the first n positive integers; see A093883. - Clark Kimberling, Jan 02 2012
All trees can be embedded in the plane, but "planar embedded" means that orientation matters but rotation doesn't. For example, the n-star with n-1 edges has n! ways to label it, but rotation removes a factor of n-1. Another example, the n-path has n! ways to label it, but rotation removes a factor of 2. - Michael Somos, Aug 19 2014

Examples

			G.f. = x + x^2 + 3*x^3 + 20*x^4 + 210*x^5 + 3024*x^6 + 55440*x^7 + 1235520*x^8 + ...
a(5) = 210 = 30 + 60 + 120 where 30 is for the star, 60 for the path, and 120 for the tree with one trivalent vertex. - _Michael Somos_, Aug 19 2014
		

References

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

Crossrefs

Programs

  • Magma
    [1] cat [Factorial(2*n-3)/Factorial(n-1): n in [2..20]]; // Vincenzo Librandi, Nov 12 2011
    
  • Maple
    1, seq((2*n-3)!/(n-1)!,n=2..30); # Robert Israel, Aug 20 2014
  • Mathematica
    Join[{1},Table[(2n-3)!/(n-1)!,{n,2,20}]] (* Harvey P. Dale, Nov 03 2011 *)
    a[ n_] := With[{m = n - 1}, If[m < 1, Boole[m == 0], m! SeriesCoefficient[ -Log[(1 + Sqrt[1 - 4 x]) / 2], {x, 0, m}]]] (* Michael Somos, Jul 01 2013 *)
    a[ n_] := If[n < 2, Boole[n == 1], (2 n - 3)! / (n - 1)!]; (* Michael Somos, Aug 19 2014 *)
    a[1] := 1; a[n_] := (-1)^(n - 1)*Sum[(-1)^k*Binomial[2*n - 3, n + k - 2]*StirlingS1[n + k - 1, k + 1], {k, 1, n - 1}]; Flatten[Table[a[n], {n, 1, 19}]] (* Detlef Meya, Jan 18 2024 *)
  • PARI
    {a(n) = n--; if( n<1, n==0, n! * polcoeff( -log( (1 + sqrt(1 - 4*x + x * O(x^n))) / 2), n))}; /* Michael Somos, Jul 01 2013 */
    
  • SageMath
    def A006963(n): return 1 if n==1 else factorial(2*n-3)/factorial(n-1)
    [A006963(n) for n in range(1,31)] # G. C. Greubel, May 23 2023

Formula

E.g.f. for a(n+1), n >= 1, log(c(x)); c(x) = g.f. for Catalan numbers A000108. - Wolfdieter Lang
Integral representation as n-th moment of a positive function on a positive half-axis, in Maple notation: a(n) = int(x^n * erfc(sqrt(x)/2)/2, x=0..infinity), n=0, 1..., where erfc(x) is the complementary error function. - Karol A. Penson, Sep 27 2001
a(n) ~ 2^(-5/2)*n^-2*2^(2*n)*e^-n*n^n. - Joe Keane (jgk(AT)jgk.org), Jun 06 2002
a(n+1) = (n+1)*(n+2)*...*(2n-1) for n>=2. - Jaroslav Krizek, Nov 09 2010
E.g.f. (A(x)-1) is reversion of exp(-x)-exp(-2*x). - Vladimir Kruchinin, Jan 30 2012
G.f.: 1 + x*G(0) where G(k) = 1 + x*(2*k+1)*(4*k+3)/(k + 1 - 4*x*(k+1)^2*(4*k+5)/(4*x*(k+1)*(4*k+5) + (2*k+3)/G(k+1) )); (continued fraction). - Sergei N. Gladkovskii, Feb 02 2013
E.g.f.: 1 + x*E(0) where E(k) = 1 + x*(2*k+1)*(4*k+3)/(2*(k + 1)^2 - 8*x*(k+1)^3*(4*k+5)/(4*x*(k+1)*(4*k+5) + (2*k+3)^2/E(k+1) )); (continued fraction). - Sergei N. Gladkovskii, Feb 02 2013
E.g.f: sqrt(1-4*x)/4 - 1/4 + 3*x/2 - x*log((1+sqrt(1-4*x))/2). - Robert Israel, Aug 20 2014
D-finite with recurrence (-n+1)*a(n) +2*(2*n-3)*(n-2)*a(n-1)=0. - R. J. Mathar, Jan 03 2018
From Amiram Eldar, Apr 03 2022: (Start)
Sum_{n>=1} 1/a(n) = 3/2 + 3*exp(1/4)*sqrt(Pi)*erf(1/2)/4, where erf is the error function.
Sum_{n>=1} (-1)^(n+1)/a(n) = 1/2 - sqrt(Pi)*erfi(1/2)/(4*exp(1/4)), where erfi is the imaginary error function. (End)
a(n) = A000407(n-2)/(n-1). - R. J. Mathar, Mar 30 2023
a(1) = 1; a(n) = (-1)^(n - 1)*Sum_{k=1..n - 1} (-1)^k*binomial(2*n - 3, n + k - 2)*Stirling1(n + k - 1, k + 1). - Detlef Meya, Jan 18 2024

A203312 Vandermonde sequence using x^2 - xy + y^2 applied to (1,2,...,n).

Original entry on oeis.org

1, 3, 147, 298116, 47460365316, 965460013501733568, 3717096745012192786213464768, 3763515081241454304168766426610670649344, 1329626784930718063722475681347135527472012731205697536
Offset: 1

Views

Author

Clark Kimberling, Jan 04 2012

Keywords

Comments

See A093883 for a discussion and guide to related sequences.

Crossrefs

Programs

  • Mathematica
    f[j_] := j; z = 12;
    v[n_] := Product[Product[f[j]^2 - f[j] f[k] + f[k]^2,
    {j, 1, k - 1}], {k, 2, n}]
    Table[v[n], {n, 1, z}]          (* A203312 *)
    Table[v[n + 1]/v[n], {n, 1, z}] (* A203513 *)
  • Python
    from operator import mul
    from functools import reduce
    def v(n): return 1 if n==1 else reduce(mul, [j**2 - j*k + k**2 for k in range(2, n + 1) for j in range(1, k)])
    print([v(n) for n in range(1, 11)]) # Indranil Ghosh, Jul 26 2017

Formula

a(n) ~ c * n^(n^2 - n - 2/3) / exp(3*n^2/2 - n*(n+1)*Pi/(2*sqrt(3)) - n), where c = Gamma(1/3) * 3^(1/12) * exp(Pi/(12*sqrt(3))) / (2^(4/3) * Pi^(4/3)) = 0.2945280196744096322469352538791946777977998766871923997662057483092872... - Vaclav Kotesovec, Nov 22 2023

A203475 a(n) = Product_{1 <= i < j <= n} (i^2 + j^2).

Original entry on oeis.org

1, 5, 650, 5525000, 5807194900000, 1226800120038480000000, 77092420109247492627600000000000, 2001314057760220784660590245696000000000000000, 28468550112906756205383102673584071297339520000000000000000000
Offset: 1

Views

Author

Clark Kimberling, Jan 02 2012

Keywords

Comments

Each term divides its successor, as in A203476.

Crossrefs

Programs

  • Magma
    [(&*[(&*[j^2 + k^2: k in [1..j]])/(2*j^2): j in [1..n]]): n in [1..20]]; // G. C. Greubel, Aug 28 2023
    
  • Maple
    a:= n-> mul(mul(i^2+j^2, i=1..j-1), j=2..n):
    seq(a(n), n=1..10);  # Alois P. Heinz, Jul 23 2017
  • Mathematica
    f[j_]:= j^2; z = 15;
    v[n_]:= Product[Product[f[k] + f[j], {j,k-1}], {k,2,n}]
    Table[v[n], {n,z}]           (* A203475 *)
    Table[v[n+1]/v[n], {n,z-1}]  (* A203476 *)
  • SageMath
    [product(product(j^2+k^2 for k in range(1,j)) for j in range(1,n+1)) for n in range(1,21)] # G. C. Greubel, Aug 28 2023

Formula

a(n) ~ c * 2^(n^2/2) * exp(Pi*n*(n+1)/4 - 3*n^2/2 + n) * n^(n*(n-1) - 3/4), where c = A323755 = sqrt(Gamma(1/4)) * exp(Pi/24) / (2*Pi)^(9/8) = 0.274528350333552903800408993482507428142383783773190451181... - Vaclav Kotesovec, Jan 26 2019

Extensions

Name edited by Alois P. Heinz, Jul 23 2017

A203673 Vandermonde sequence using x^2 + xy + y^2 applied to (1,4,9,...,n^2).

Original entry on oeis.org

1, 21, 254163, 11213968422384, 6451450005117349260375984, 127857993263632065817610313129228311433216, 191199773886534869435599958788731398661833328276349525268803584
Offset: 1

Views

Author

Clark Kimberling, Jan 04 2012

Keywords

Comments

See A093883 for a discussion and guide to related sequences.

Crossrefs

Cf. A367550.

Programs

  • Mathematica
    f[j_] := j^2; z = 12;
    u[n_] := Product[f[j]^2 + f[j] f[k] + f[k]^2, {j, 1, k - 1}]
    v[n_] := Product[u[n], {k, 2, n}]
    Table[v[n], {n, 1, z}]          (* A203673 *)
    Table[v[n + 1]/v[n], {n, 1, z}] (* A203674 *)

Formula

From Vaclav Kotesovec, Nov 22 2023: (Start)
a(n) = A203012(n) * A203312(n).
a(n) ~ c * 3^(n*(3*n+1)/4) * n^(2*n^2 - 2*n - 3/2) / exp(3*n^2 - n*(n+1)*Pi*sqrt(3)/4 - 2*n), where c = Gamma(1/3)^(3/2) * 3^(7/24) * exp(Pi/(8*sqrt(3))) / (2^(5/2) * Pi^(5/2)) = 0.076580853261060033865281896312127877504662138809362419847380161198324... (End)

A080358 Value of Vandermonde determinant for the first n prime numbers: V[prime(1), ..., prime(n)].

Original entry on oeis.org

1, 1, 1, 6, 240, 414720, 4379443200, 2648687247360000, 11619303595714805760000, 4047756373260469165621248000000, 311107430628520522709128328175943680000000, 152539657943794787580793302587123569672794931200000000
Offset: 0

Views

Author

Labos Elemer, Feb 19 2003

Keywords

Comments

The value of the Vandermonde determinant is unchanged if the numbers are shifted by an arbitrary constant c, i.e., V[prime(1), ..., prime(n)] = V[prime(1)-c, ..., prime(n)-c].
For a guide to related sequences, see A093883. - Clark Kimberling, Jan 03 2012

Examples

			a(1)=1 corresponds to 1 X 1 V-matrix, while a(2)=1 is computed from a 2 X 2 matrix.
n = 2: a(2) = prime(2) - prime(1) = 3 - 2 = 1;
n = 3: a(3) = (5-3)*(5-2)*(3-2) = 2*3*1 = 6; ...
n = 6: a(6) = (13-11)*(13-7)*(13-5)*(13-3)*(13-2)*(11-7)*(11-5)*(11-3)*(11-2)*(7-5)*(7-3)*(7-2)*(5-3)*(5-2)*(3-2) = 2*6*8*10*11*4*6*8*9*2*4*5*2*3*1 = 10560*1728*40*6*1 = 4379443200.
		

Crossrefs

Programs

  • Maple
    with(LinearAlgebra):
    a:= n-> Determinant(Matrix(n, (i,j)-> ithprime(i)^(j-1))):
    seq(a(n), n=0..15);  # Alois P. Heinz, Jul 22 2017
  • Mathematica
    b[x_] := Prime[x] d[x_] := b[x+1]-b[x] t[m_] := b[m+1]-Table[b[x], {x, 1, m}] pt[x_] := Apply[Times, t[x]] va[x_] := Apply[Times, Table[pt[w], {w, 1, x}]] Table[va[j], {j, 1, 10}]

Formula

a(n) = Product_{i, j, i>j} (prime(i) - prime(j)). a(n) is the product of binomial(n, 2) prime differences of not necessarily consecutive primes.
For n > 1, a(n) = sqrt(Delta_n), where Delta_n is the discriminant of the polynomial (x - 2)*(x - 3)*...*(x - prime(n)). - Thomas Ordowski, Mar 15 2023

A203012 Vandermonde sequence using x^2 + xy + y^2 applied to (1,2,...,n).

Original entry on oeis.org

1, 7, 1729, 37616124, 135933424914924, 132432199651531695045312, 51437933151214684812682944045953088, 11056394929890243558409721156996503083526683082752, 1743892714865607005898689849291524734866677095031979100765833773056
Offset: 1

Views

Author

Clark Kimberling, Jan 04 2012

Keywords

Comments

See A093883 for a discussion and guide to related sequences.

Examples

			a(1)=1
a(2)=1^2+1*2+2^2=7
a(3)=(1^2+1*2+2^2)(1^3+1*3+3^2)(2^2+2*3+3^2)=1729.
		

Crossrefs

Programs

  • Mathematica
    f[j_] := j; z = 12;
    v[n_] := Product[Product[f[j]^2 + f[j] f[k] + f[k]^2,
    {j, 1, k - 1}], {k, 2, n}]
    Table[v[n], {n, 1, z}]          (* A203012 *)
    Table[v[n + 1]/v[n], {n, 1, z}] (* A203158 *)

Formula

a(n) ~ c * n^(n^2 - n - 5/6) * 3^(n*(3*n+1)/4) / exp(3*n^2/2 - n - n*(n+1)*Pi / (4*sqrt(3))), where c = sqrt(Gamma(1/3)) * 3^(5/24) * exp(Pi/(24*sqrt(3))) / (2^(7/6) * Pi^(7/6)) = 0.26001211479205772659823692637002123572622409280442625312217301129630097... - Vaclav Kotesovec, Nov 22 2023

A203311 Vandermonde determinant of (1,2,3,...,F(n+1)), where F=A000045 (Fibonacci numbers).

Original entry on oeis.org

1, 1, 1, 2, 48, 30240, 1596672000, 18172937502720000, 122457316443772566896640000, 1284319496829094129116119090331648000000, 55603466527142141932748234118927499493985767915520000000, 26110840958525805673462196263372614726154694067746586937781385166848000000000
Offset: 0

Views

Author

Clark Kimberling, Jan 01 2012

Keywords

Comments

Each term divides its successor, as in A123741. Each term is divisible by the corresponding superfactorial, A000178(n), as in A203313.
For a signed version, see A123742. For a guide to related sequences, including sequences of Vandermonde permanents, see A093883.

Examples

			v(4) = (2-1)*(3-1)*(3-2)*(5-1)*(5-2)*(5-3).
		

Crossrefs

Programs

  • Maple
    with(LinearAlgebra): F:= combinat[fibonacci]:
    a:= n-> Determinant(VandermondeMatrix([F(i)$i=2..n+1])):
    seq(a(n), n=0..12);  # Alois P. Heinz, Jul 23 2017
  • Mathematica
    f[j_] := Fibonacci[j + 1]; z = 15;
    v[n_] := Product[Product[f[k] - f[j], {j, 1, k - 1}], {k, 2, n}]
    d[n_] := Product[(i - 1)!, {i, 1, n}]
    Table[v[n], {n, 1, z}]                (* A203311 *)
    Table[v[n + 1]/v[n], {n, 1, z - 1}]   (* A123741 *)
    Table[v[n]/d[n], {n, 1, 13}]          (* A203313 *)
  • Python
    from sympy import fibonacci, factorial
    from operator import mul
    from functools import reduce
    def f(j): return fibonacci(j + 1)
    def v(n): return 1 if n==1 else reduce(mul, [reduce(mul, [f(k) - f(j) for j in range(1, k)]) for k in range(2, n + 1)])
    print([v(n) for n in range(1, 16)]) # Indranil Ghosh, Jul 26 2017

Formula

a(n) ~ c * d^n * phi^(n^3/3 + n^2/2) / 5^(n^2/4), where phi = A001622 = (1+sqrt(5))/2 is the golden ratio, d = 0.120965069090607877853843907542896935455225485213927649233956250456604334... and c = 197.96410442333389877538426269... - Vaclav Kotesovec, Apr 08 2021

A203482 a(n) = Product_{1 <= i < j <= n} (i! + j!).

Original entry on oeis.org

1, 3, 168, 3276000, 877449500928000, 207244701437748852512194560000, 4000516840149319128119305958853265913416777728000000, 796608816253064941944831363792070377592412324940256242675178274726476775424000000000
Offset: 1

Views

Author

Clark Kimberling, Jan 03 2012

Keywords

Comments

Each term divides its successor, as in A203483.
See A093883 for a guide to related sequences.

Crossrefs

Programs

  • Magma
    [(&*[(&*[Factorial(j) + Factorial(k): k in [1..j]])/(2*Factorial(j)): j in [1..n]]): n in [1..20]]; // G. C. Greubel, Aug 29 2023
    
  • Maple
    a:= n-> mul(mul(i!+j!, i=1..j-1), j=2..n):
    seq(a(n), n=1..10);  # Alois P. Heinz, Jul 23 2017
  • Mathematica
    (* First program *)
    f[j_]:= j!; z = 10;
    v[n_]:= Product[Product[f[k] + f[j], {j, k-1}], {k, 2, n}]
    d[n_]:= Product[(i-1)!, {i, n}]  (* A000178 *)
    Table[v[n], {n, z}]              (* A203482 *)
    Table[v[n+1]/v[n], {n, z-1}]     (* A203483 *)
    Table[v[n]/d[n], {n, 10}]        (* A203510 *)
    (* Second program *)
    Table[Product[j!+k!, {j,n}, {k,j-1}], {n,15}] (* G. C. Greubel, Aug 29 2023 *)
  • SageMath
    [product(product(factorial(j) + factorial(k) for k in range(1,j)) for j in range(1,n+1)) for n in range(1,16)] # G. C. Greubel, Aug 29 2023

Formula

a(n) ~ c * n^(n^3/3 + n^2/4 - 7*n/12 + 5/8) * (2*Pi)^(n*(n-1)/4) / exp(4*n^3/9 - n^2/8 - n), where c = 0.488888619502150098591650327163991582267254151817880403495924251381414248582... - Vaclav Kotesovec, Nov 20 2023

Extensions

Name edited by Alois P. Heinz, Jul 23 2017
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