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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A296591 a(n) = Product_{k=0..n} (n + k)!.

Original entry on oeis.org

1, 2, 288, 12441600, 421382062080000, 23120161750363668480000000, 3683853104727992382799761899520000000000, 2777528195026874073410445622205453260145295360000000000000
Offset: 0

Views

Author

Vaclav Kotesovec, Dec 16 2017

Keywords

Crossrefs

Programs

  • Maple
    a:= proc(n) option remember; `if`(n=0, 1,
          a(n-1) *(2*n-1)! *(2*n)! /(n-1)!)
        end:
    seq(a(n), n=0..7);  # Alois P. Heinz, Jul 11 2024
  • Mathematica
    Table[Product[(n + k)!, {k, 0, n}], {n, 0, 10}]
    Table[Product[(2*n - k)!, {k, 0, n}], {n, 0, 10}]
    Table[BarnesG[2*n + 2]/BarnesG[n + 1], {n, 0, 10}]

Formula

a(n) = BarnesG(2*n + 2) / BarnesG(n + 1).
a(n) ~ 2^(2*n^2 + 5*n/2 + 11/12) * n^((n+1)*(3*n+1)/2) * Pi^((n+1)/2) / exp(9*n^2/4 + 2*n).

Extensions

Missing a(0)=1 inserted by Georg Fischer, Nov 18 2021

A249433 Integers n such that n! does not divide the product of elements on row n of Pascal's triangle.

Original entry on oeis.org

3, 5, 7, 8, 9, 11, 13, 14, 15, 17, 19, 20, 21, 23, 24, 25, 26, 27, 29, 31, 32, 33, 34, 37, 38, 41, 43, 44, 45, 47, 48, 49, 50, 51, 53, 54, 55, 56, 57, 59, 61, 63, 64, 65, 67, 68, 69, 71, 73, 74, 75, 76, 77, 80, 81, 84, 85, 86, 87, 90, 91, 92, 93, 94, 95, 97, 98, 99, 101, 103, 105, 109, 110, 111, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 127, 128
Offset: 1

Views

Author

Antti Karttunen, Nov 02 2014

Keywords

Comments

Integers n such that A249151(n) < n.
Equally: Integers n such that A249431(n) is negative.

Examples

			See the examples at A249434.
		

Crossrefs

Complement: A249434.
Subsequences: A000225, A024023, A024049, etc., (after their two initial terms, i.e. A249435 without its initial zero is also a subsequence), A249424, A249436.

A056606 Squarefree kernel of lcm(binomial(n,0), ..., binomial(n,n)).

Original entry on oeis.org

1, 1, 2, 3, 6, 10, 30, 105, 70, 42, 210, 2310, 2310, 4290, 6006, 15015, 30030, 170170, 510510, 1939938, 1385670, 881790, 9699690, 223092870, 44618574, 17160990, 74364290, 31870410, 223092870, 6469693230, 6469693230, 100280245065
Offset: 0

Views

Author

Labos Elemer, Aug 07 2000

Keywords

Comments

Also squarefree kernel of A001142; row products in table A256113. - Reinhard Zumkeller, Mar 21 2015
a(2372) has 1001 decimal digits. - Michael De Vlieger, Jul 14 2017
Also the squarefree kernel of the cumulative product of n^n/n!. - Peter Luschny, Dec 21 2019
Conjecture: the few odd values belong to A070826. - Bill McEachen, Jun 24 2023
And their indices appear to be A007053. - Michel Marcus, Jul 01 2023

Examples

			a(7) = 105 because lcm(1, 7, 21, 35) = 105 is already squarefree.
a(0) = 1 because n^n/n! = 1 for the integer n = 0. - _Peter Luschny_, Dec 21 2019
		

Crossrefs

Programs

  • Haskell
    a056606 = a007947 . a001142  -- Reinhard Zumkeller, Mar 21 2015
    
  • Maple
    h := n -> mul(k^k/factorial(k), k=0..n):
    rad := n -> mul(k, k = numtheory[factorset](n)):
    seq(rad(h(n)), n=0..31); # Peter Luschny, Dec 21 2019
  • Mathematica
    Table[Apply[Times, FactorInteger[Product[k^(2 k - 1 - n), {k, n}]][[All, 1]]], {n, 0, 31}] (* or *)
    Table[Apply[Times, FactorInteger[Apply[LCM, Range@ n]/n][[All, 1]]], {n, 1, 32}] (* Michael De Vlieger, Jul 14 2017 *)
  • PARI
    rad(n) = factorback(factorint(n)[, 1]); \\ A007947
    a(n) = rad(lcm(vector(n+1, k, binomial(n,k-1)))); \\ Michel Marcus, Jun 24 2023

Formula

a(n) = A007947(A002944(n+1)). - Michel Marcus, Dec 21 2019
a(n) = radical(hyperfactorial(n)/superfactorial(n)) = A007947(A002109(n)/ A000178(n)) for n >= 0. - Peter Luschny, Dec 21 2019

Extensions

Extended with a(0) = 1 by Peter Luschny, Dec 21 2019

A004788 Number of distinct prime divisors of the numbers in row n of Pascal's triangle.

Original entry on oeis.org

0, 0, 1, 1, 2, 2, 3, 3, 3, 3, 4, 5, 5, 5, 5, 5, 6, 6, 7, 7, 7, 7, 8, 9, 8, 8, 8, 8, 9, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 13, 13, 14, 13, 14, 15, 14, 14, 14, 14, 15, 15, 15, 16, 15, 15, 16, 17, 17, 17, 18, 17, 17, 17, 18, 18, 18, 19, 19, 20, 20
Offset: 0

Views

Author

Keywords

Comments

Also the number of prime divisors of A002944(n) = lcm_{j=0..floor(n/2)} binomial(n,j).
The terms are increasing by intervals, then decrease once. The local maxima are obtained for 23, 44, 47, 55, 62, 79, 83, 89, 104, 119, 131, 134, 139, 143, .... - Michel Marcus, Mar 21 2013
a(A004789(n)) = n and a(m) != n for m < A004789(n). - Reinhard Zumkeller, Mar 16 2015

Crossrefs

Programs

  • Haskell
    a004788 = a001221 . a001142  -- Reinhard Zumkeller, Mar 16 2015
  • Mathematica
    Table[prd = Product[Binomial[n, k], {k, 0, n}]; If[prd == 1, 0, Length[FactorInteger[prd]]], {n, 0, 100}] (* T. D. Noe, Mar 21 2013 *)
  • PARI
    a(n) = {sfp = Set(); for (k=1, n-1, sfp = setunion(sfp, Set(factor(binomial(n, k))[,1]))); return (length(sfp));} \\ Michel Marcus, Mar 21 2013
    

Formula

a(n) = A001221(A001142(n)). - Reinhard Zumkeller, Mar 16 2015

A051459 Number of orderings of the subsets of a set with n elements that are compatible with the subsets' sizes; i.e., if A, B are two subsets with A <= B then Card(A) <= Card(B).

Original entry on oeis.org

1, 1, 2, 36, 414720, 189621927936000000, 2156695499113014719143826715127578624000000000000
Offset: 0

Views

Author

Yuval Dekel (dekelyuval(AT)hotmail.com), Nov 15 2003

Keywords

Comments

a(7) has 127 digits and too large to include in sequence. - Ray Chandler, Nov 22 2003
From Valentin Bakoev, Nov 20 2017, May 17 2019: (Start)
a(n) is the number of possible orderings of the vectors of the n-dimensional Boolean cube (hypercube) {0,1}^n in accordance with their (Hamming) weights. For arbitrary vectors u, v of {0, 1}^n, if wt(u)
a(n) is also the number of all possible topological orders (sortings) of the directed acyclic graph (DAG) defined by the same poset: {0,1}^n and the relation weight order as it is defined and explained above.
Both comments correspond to the name of the sequence since the corresponding Boolean algebras are isomorphic. (End)

Crossrefs

Programs

  • Maple
    a:= n-> mul(binomial(n, i)!, i=0..n):
    seq(a(n), n=0..6);  # Alois P. Heinz, Nov 20 2017
  • Mathematica
    Array[Product[Binomial[#, i]!, {i, #}] &, 7, 0] (* Michael De Vlieger, Nov 20 2017 *)
  • Maxima
    a(n):= prod(binomial(n,k)!,k,0,n); /* Valentin Bakoev, May 17 2019 */
    
  • PARI
    a(n) = prod(k=0, n, binomial(n, k)!); \\ Michel Marcus, May 18 2019

Formula

a(n) = C(n, 0)! * C(n, 1)! * C(n, 2)! * ... * C(n, n)! = A000722(n) / A022914(n).
log(a(n)) ~ log(2) * n * 2^n. - Vaclav Kotesovec, Nov 24 2023

Extensions

More terms from Ray Chandler, Nov 22 2003
a(0)=1 prepended by Alois P. Heinz, Nov 20 2017

A249345 The exponent of the highest power of 5 dividing the product of the elements on the n-th row of Pascal's triangle.

Original entry on oeis.org

0, 0, 0, 0, 0, 4, 3, 2, 1, 0, 8, 6, 4, 2, 0, 12, 9, 6, 3, 0, 16, 12, 8, 4, 0, 44, 38, 32, 26, 20, 43, 36, 29, 22, 15, 42, 34, 26, 18, 10, 41, 32, 23, 14, 5, 40, 30, 20, 10, 0, 88, 76, 64, 52, 40, 82, 69, 56, 43, 30, 76, 62, 48, 34, 20, 70, 55, 40, 25, 10, 64, 48, 32, 16, 0
Offset: 0

Author

Antti Karttunen, Oct 28 2014

Keywords

Crossrefs

Programs

  • Mathematica
    A249345[n_] := Sum[#*((#+1)*5^k - n - 1) & [Floor[n/5^k]], {k, Floor[Log[5, n]]}];
    Array[A249345, 100, 0] (* Paolo Xausa, Feb 11 2025 *)
  • PARI
    allocatemem(234567890);
    A249345(n) = sum(k=0, n, valuation(binomial(n, k), 5));
    for(n=0, 3124, write("b249345.txt", n, " ", A249345(n)));
    
  • Scheme
    (define (A249345 n) (A112765 (A001142 n)))
    
  • Scheme
    (define (A249345 n) (add (lambda (n) (A112765 (A007318 n))) (A000217 n) (A000096 n)))
    (define (add intfun lowlim uplim) (let sumloop ((i lowlim) (res 0)) (cond ((> i uplim) res) (else (sumloop (+ 1 i) (+ res (intfun i)))))))

Formula

a(n) = A112765(A001142(n)).
a(n) = Sum_{k=0..n} A112765(binomial(n,k)).
a(n) = Sum_{i=1..n} (2*i-n-1)*v_5(i), where v_5(i) = A112765(i) is the exponent of the highest power of 5 dividing i. - Ridouane Oudra, Jun 02 2022
a(n) = Sum_{k=1..floor(log_5(n))} t*((t+1)*5^k - n - 1), where t = floor(n/(5^k)). - Paolo Xausa, Feb 11 2025, derived from Ridouane Oudra's formula above.

A249347 The exponent of the highest power of 7 dividing the product of the elements on the n-th row of Pascal's triangle.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 6, 5, 4, 3, 2, 1, 0, 12, 10, 8, 6, 4, 2, 0, 18, 15, 12, 9, 6, 3, 0, 24, 20, 16, 12, 8, 4, 0, 30, 25, 20, 15, 10, 5, 0, 36, 30, 24, 18, 12, 6, 0, 90, 82, 74, 66, 58, 50, 42, 89, 80, 71, 62, 53, 44, 35, 88, 78, 68, 58, 48, 38, 28, 87, 76, 65, 54, 43, 32, 21, 86, 74, 62, 50, 38, 26, 14, 85, 72, 59, 46, 33, 20, 7, 84, 70, 56, 42, 28, 14, 0
Offset: 0

Author

Antti Karttunen, Oct 28 2014

Keywords

Crossrefs

Programs

  • Mathematica
    A249347[n_] := Sum[#*((#+1)*7^k - n - 1) & [Floor[n/7^k]], {k, Floor[Log[7, n]]}];
    Array[A249347, 100, 0] (* Paolo Xausa, Feb 08 2025 *)
  • PARI
    allocatemem(234567890);
    A249347(n) = sum(k=0, n, valuation(binomial(n, k), 7));
    for(n=0, 2400, write("b249347.txt", n, " ", A249347(n)));
    
  • Scheme
    (define (A249347 n) (A214411 (A001142 n)))
    
  • Scheme
    (define (A249347 n) (add (lambda (n) (A214411 (A007318 n))) (A000217 n) (A000096 n)))
    (define (add intfun lowlim uplim) (let sumloop ((i lowlim) (res 0)) (cond ((> i uplim) res) (else (sumloop (+ 1 i) (+ res (intfun i)))))))

Formula

a(n) = A214411(A001142(n)).
a(n) = Sum_{k=0..n} A214411(binomial(n,k)).
a(n) = Sum_{i=1..n} (2*i-n-1)*v_7(i), where v_7(i) = A214411(i) is the exponent of the highest power of 7 dividing i. - Ridouane Oudra, Jun 03 2022
a(n) = Sum_{k=1..floor(log_7(n))} t*((t+1)*7^k - n - 1), where t = floor(n/(7^k)). - Paolo Xausa, Feb 09 2025, derived from Ridouane Oudra's formula above.

A073225 a(n) = ceiling(n^n/n!).

Original entry on oeis.org

1, 1, 2, 5, 11, 27, 65, 164, 417, 1068, 2756, 7148, 18614, 48639, 127464, 334865, 881658, 2325751, 6145597, 16263867, 43099805, 114356612, 303761261, 807692035, 2149632062, 5726042116, 15264691108, 40722913455, 108713644517
Offset: 0

Author

Michael Somos, Jul 22 2002

Keywords

Comments

The van der Waerden conjecture, now a theorem thanks to Egorycev, states that the permanent of any n X n doubly stochastic matrix is >= n!/n^n, with equality iff the matrix has all entries equal to 1/n.
Therefore the reciprocal of the permanent of any n X n doubly stochastic matrix is bounded from above by n^n/n! and this sequence.
n^n/n! = A001142(n)/A001142(n-1), where A001142(n) is product{k=0 to n} C(n,k) (where C() is a binomial coefficient). - Leroy Quet, May 01 2004

Examples

			G.f.: 1 + x + 2*x^2 + 5*x^3 + 11*x^4 + 27*x^5 + 65*x^6 + 164*x^7 + 417*x^8 + ...
		

References

  • G. P. Egorycev, Solution of the van der Waerden problem for permanents (Russian), Preprint IFSO-13 M. Akad. Nauk SSSR Sibirsk. Otdel., Inst. Fiz., Krasnoyarsk, 1980. 12 pp. Math. Rev. 82e:15006.
  • J. H. van Lint, R. M. Wilson, A Course in Combinatorics, Cambridge Univ. Press, 1992. p. 86.

Crossrefs

Programs

  • Magma
    [Ceiling(n^n/Factorial(n)): n in [0..50]]; // G. C. Greubel, May 29 2018
  • Mathematica
    Join[{1}, Table[Ceiling[n^n/n!], {n,1,50}]] (* G. C. Greubel, May 29 2018 *)
  • PARI
    {a(n) = ceil(n^n / n!)}
    

A208650 Number of constant paths through the subset array of {1,2,...,n}; see Comments.

Original entry on oeis.org

1, 2, 6, 36, 480, 15000, 1134000, 211768200, 99131719680, 117595223746560, 356467003200000000, 2779532232516963000000, 56049508602150185041920000, 2935889842347365340037522521600
Offset: 1

Author

Clark Kimberling, Mar 01 2012

Keywords

Comments

Let I(n)={1,2,...,n}. Arrange the subsets of I(n) in an array S(n) of n rows, where row k consists of all the numbers in all the k-element subsets, including repetitions. Each i in I(n) occurs C(n-1,k-1) times in row k of S(n); index these occurrences as
...
(k,1,1),(k,1,2),...,(k,1,r),(k,2,1),...,(k,2,r),...,(k,n,1),...,(k,n,r),
...
where r=C(n-1,k-1).
Definitions:
(1) A path through I(n) is an n-tuple of triples, ((1,i(1),j(1)), (2,i(2),j(2)), ..., (n,i(n),j(n))), formed from the above indexing of the numbers in S(n).
(2) The trace of such a path p is the n-tuple (i(1),i(2),...,i(n)).
(3) The range of p is the set {i(1),i(2),...,i(n)}.
(4) Path p has property P if its trace or range has property P.
...
Guide to sequences which count paths according to selected properties:
property................................sequence
range = {1}.............................A001142(n-1)
constant (range just one element).......A208650
range = {1,2,...,n}.....................A208651
palindromic.............................A208654
palindromic with i(1)=1.................A208655

Examples

			Taking n=3:
row 1:  {1},{2},{3} ---------> 1,2,3
row 2:  {1,2},{1,3},{2,3} ---> 1,1,2,2,3,3
row 3:  {1,2,3} -------------> 1,2,3
3 ways to choose a number from row 1,
2 ways to choose same number from row 2,
1 way to choose same number from row 3.
Total:  a(3) = 1*2*3 = 6 paths.
		

Crossrefs

Cf. A208651.

Programs

  • Mathematica
    p[n_]:=Product[Binomial[n-1,k],{k,1,n-1}]
    Table[p[n],{n,1,20}]    (* A001142(n-1) *)
    Table[p[n]*n,{n,1,20}]  (* A208650 *)
    Table[p[n]*n!,{n,1,20}] (* A208651 *)

Formula

a(n) = n*Product_{k=1..n-1} binomial(n-1,k). - Jason Yuen, Feb 18 2025

A249346 The exponent of the highest power of 6 dividing the product of the elements on the n-th row of Pascal's triangle.

Original entry on oeis.org

0, 0, 0, 0, 1, 0, 4, 0, 0, 10, 10, 4, 13, 8, 3, 0, 6, 0, 28, 20, 12, 24, 15, 6, 20, 10, 0, 16, 47, 22, 26, 0, 30, 48, 33, 18, 73, 56, 39, 40, 42, 24, 47, 28, 9, 54, 57, 16, 62, 40, 18, 46, 23, 0, 82, 32, 84, 94, 87, 44, 92, 52, 36, 0, 102, 72, 107, 76, 45, 82, 50, 18, 128, 94, 60, 100, 65, 30, 72, 36, 0
Offset: 0

Author

Antti Karttunen, Oct 31 2014

Keywords

Comments

Sounds good with MIDI player set to FX-7.

Crossrefs

Minimum of terms A187059(n) and A249343(n).

Programs

  • Haskell
    a249346 = a122841 . a001142  -- Reinhard Zumkeller, Mar 16 2015
  • Mathematica
    IntegerExponent[#,6]&/@Times@@@Table[Binomial[n,k],{n,0,80},{k,0,n}] (* Harvey P. Dale, Nov 21 2023 *)
  • PARI
    A249346(n) = { my(b, s2, s3); s2 = 0; s3 = 0; for(k=0, n, b = binomial(n, k); s2 += valuation(b, 2); s3 += valuation(b, 3)); min(s2,s3); };
    for(n=0, 7775, write("b249346.txt", n, " ", A249346(n)));
    
  • Scheme
    (define (A249346 n) (min (A187059 n) (A249343 n)))
    
  • Scheme
    (define (A249346 n) (A122841 (A001142 n)))
    

Formula

a(n) = min(A187059(n), A249343(n)).
a(n) = A122841(A001142(n)).
Other identities:
a(n) = 0 when A249151(n) < 3.
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