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 1-8 of 8 results.

A375178 a(n) = Sum_{k = 0..n-1} binomial(n+k-1, k)^3 (same as A112028 with an extra 0 at the start).

Original entry on oeis.org

0, 1, 9, 244, 9065, 389376, 18188478, 897376152, 46011772521, 2427553965160, 130930630643384, 7186614533569296, 400132290102421214, 22543708920891189136, 1282873288801683197250, 73628947696550668509744, 4257138240245923453355625, 247733479854085081062353400, 14498252738780732999484606360
Offset: 0

Views

Author

Peter Bala, Aug 03 2024

Keywords

Comments

Compare with the identity Sum_{k = 0..n-1} binomial(n+k-1, k) = (1/2) * binomial(2*n, n) = (1/2) * A000984(n) for n >= 1.
The central binomial coefficients satisfy the supercongruence (1/2) * binomial(2*p, p) == 1 (mod p^3) for all primes p >= 5 (Wolstenholme's theorem).
For prime p, binomial(p+k-1, k) == 0 (mod p) for 1 <= k <= p-1. It follows that a(p) == 1 (mod p^3) for all primes p. We conjecture that, in fact, the stronger congruence a(p) == 1 (mod p^5) holds for all primes p >= 7.
Further, we conjecture that for r >= 2 and prime p >= 5, a(p^r) == a(p^(r-1)) (mod p^(3*r+3)).
More generally, for a positive integer m, define a sequence {b_m(n) : n >= 0} by setting b_m(n) = Sum_{k = 0..n-1} binomial(n+k-1, k)^(2*m+1). Then the congruence b_m(p) == 1 (mod p^(2*m+1)) clearly holds for all primes p. We conjecture that the stronger supercongruence b_m(p) == 1 (mod p^(2*m+3)) holds for all primes p >= 2*m + 5, and for r >= 2, the supercongruence b_m(p^r) == b_m(p^(r-1)) (mod p^(3*r+2*m+1)) also holds for all primes p >= 2*m + 5.
Essentially a duplicate of A112028.

Examples

			Examples of supercongruences:
a(7) - a(1) = 897376152 - 1 = (7^5)*107*499 == 0 (mod 7^5)
a(11) - a(1) = 7186614533569296 - 1 = 5*(11^5)*8924644409 == 0 (mod 11^5).
		

Crossrefs

Programs

  • Maple
    seq(add( binomial(n+k-1, k)^3, k = 0..n-1), n = 0..20);

Formula

a(n) = Sum_{k = 0..n-1} (-1)^k * binomial(-n, k)^3.
a(n) ~ 2^(6*n-3)/(7*Pi^(3/2)*n^(3/2)). - Vaclav Kotesovec, Aug 03 2024

A112029 a(n) = Sum_{k=0..n} binomial(n+k, k)^2.

Original entry on oeis.org

1, 5, 46, 517, 6376, 82994, 1119210, 15475205, 217994860, 3115374880, 45035696036, 657153097330, 9663914317396, 143050882063262, 2129448324373546, 31853280798384645, 478503774600509620, 7215090439396842572, 109154411037070011504, 1656268648035559711392
Offset: 0

Views

Author

N. J. A. Sloane, Nov 28 2005

Keywords

Crossrefs

Programs

  • Magma
    [(&+[Binomial(n+j, j)^2: j in [0..n]]): n in [0..20]]; // G. C. Greubel, Jul 06 2021
    
  • Maple
    f := 64*x^2/(16*x-1); S := sqrt(x)*sqrt(4-x);
    H := ((10*x-5/8)*hypergeom([1/4,1/4],[1],f)-(21*x-21/8)*hypergeom([1/4,5/4],[1],f))/(S*(1-16*x)^(5/4));
    ord := 30;
    ogf := series(int(series(H,x=0,ord),x)/S,x=0,ord);
    # Mark van Hoeij, Mar 27 2013
  • Mathematica
    Table[Sum[Binomial[n+k,k]^2, {k,0,n}], {n,0,20}] (* Vaclav Kotesovec, Nov 23 2012 *)
  • PARI
    a(n) = sum(k=0, n, binomial(n+k, k)^2); \\ Michel Marcus, Jul 07 2021
  • Sage
    [sum(binomial(n+j, j)^2 for j in (0..n)) for n in (0..20)] # G. C. Greubel, Jul 06 2021
    

Formula

a(n) ~ 2^(4*n+2)/(3*Pi*n). - Vaclav Kotesovec, Nov 23 2012
Recurrence: 2*(2*n+1)*(21*n-13)*n^2*a(n) = (1365*n^4 - 1517*n^3 + 240*n^2 + 216*n - 64)*a(n-1) - 4*(n-1)*(2*n-1)^2*(21*n+8)*a(n-2). - Vaclav Kotesovec, Nov 23 2012
G.f.: see Maple code. - Mark van Hoeij, Mar 27 2013
a(p-1) == 1 (mod p^3) for all primes p >= 5. See the comments in A173774. - Peter Bala, Jul 12 2024
a(n-1) = 1/(4*n) * binomial(2*n, n)^2 * ( 1 + 3*((n - 1)/(n + 1))^3 + 5*((n - 1)*(n - 2)/((n + 1)*(n + 2)))^3 + 7*((n - 1)*(n - 2)*(n - 3)/((n + 1)*(n + 2)*(n + 3)))^3 + ... ) for n >= 1. - Peter Bala, Jul 22 2024
a(m*p^r - 1) == a(m*p^(r-1) - 1) (mod p^(3*r)) for all primes p >= 5 and positive integers m and r. See Coster, Theorem 4. - Peter Bala, Nov 29 2024
a(n) = A110197(2n,n). - Alois P. Heinz, Mar 21 2025

A219562 a(n) = Sum_{k=0..n} binomial(n+k,k)^4.

Original entry on oeis.org

1, 17, 1378, 170257, 25561876, 4294835666, 776487013506, 147812510671121, 29234435383857304, 5955068493838815892, 1241820686691538181636, 263946916625793118532050, 56996643356459050103185444, 12473214064899644269110156626, 2760963661677614009262282769378
Offset: 0

Views

Author

Vaclav Kotesovec, Nov 23 2012

Keywords

Crossrefs

Programs

  • Maple
    q := x-4+I*((x+4)*(16-x))^(1/2);
    f := x*(q/8)^4;
    s := ((q-2)/(8*I-6))^(1/4);
    y1 := hypergeom([1/8, 1/8], [3/4], f) * s / x^(1/8);
    r := 2/(x*((x+4)*(16-x))^(1/2)*y1^2);
    h := hypergeom([1/2, 1/2, 1/2, 1/2],[1, 1, 1],256*x);
    u := (15*(223*x+72)*x^2*diff(h,x,x,x)+(14579*x+3226)*x*diff(h,x,x)
    +(9969*x+1002)*diff(h,x)+320*h)/(16*(16-x)*(x+4)*x^2);
    ogf := y1^2*Int(r*(1+Int(r*Int(u/(r*y1)^2,x),x)),x) ;
    # Check o.g.f. by computing a series expansion:
    SER := proc(a,x) series(a,x,20) end:
    INT := proc(a,x) int(SER(a,x),x) end:
    SER(eval(ogf, Int = INT),x); # Mark van Hoeij, Apr 02 2013
  • Mathematica
    Table[Sum[Binomial[n+k,k]^4, {k,0,n}], {n,0,20}]
  • PARI
    a(n) = sum(k=0, n, binomial(n+k,k)^4); \\ Michel Marcus, Jul 15 2022

Formula

a(n) ~ 2^(8*n+4)/(15*Pi^2*n^2).
Recurrence: 4*(n-1)*(4*n-1)*(4*n+1)*(279825*n^6 - 2240985*n^5 + 7416081*n^4 - 12962383*n^3 + 12597634*n^2 - 6438500*n + 1347304)*n^4*a(n) = 2*(n-1)*(2290647450*n^12 - 22926837585*n^11 + 100717526436*n^10 - 254986993727*n^9 + 410380920831*n^8 - 435959897978*n^7 + 305660392723*n^6 - 134977315842*n^5 + 31413259700*n^4 + 2833672*n^3 - 2076143616*n^2 + 500898816*n - 39813120)*a(n-1) + (859902225*n^13 - 10755967005*n^12 + 60090860763*n^11 - 197381561581*n^10 + 422055067481*n^9 - 613861172995*n^8 + 615013106513*n^7 - 418396400175*n^6 + 182810864162*n^5 - 42759392772*n^4 + 146171272*n^3 + 2813432832*n^2 - 691172352*n + 55738368)*a(n-2) - 16*(n-2)^3*(2*n-3)^4*(279825*n^6 - 562035*n^5 + 408531*n^4 - 111409*n^3 - 5504*n^2 + 7968*n - 1024)*a(n-3).
G.f. as an expression in terms of 2F1 and 4F3 functions is given in the Maple program below. - Mark van Hoeij, Apr 02 2013
From Peter Bala, Nov 29 2024: (Start)
Conjecture: a(p-1) == 1 (mod p^5) for prime p >= 7 (checked up to p = 499). Coster, Theorem 4, proves that a(p-1) == 1 (mod p^3) for primes p >= 5.
Conjecture: for r >= 2, the supercongruence a(p^r - 1) == a(p^(r-1) - 1) (mod p^(3*r+3)) may hold for all primes p >= 5. Coster, Theorem 4, proves that a(p^r -1) == a(p^(r-1) - 1) (mod p^(3*r)) for r >= 2 and all primes p >= 5. (End)

A219563 Sum(binomial(n+k,k)^5, k=0..n).

Original entry on oeis.org

1, 33, 8020, 3301025, 1733984376, 1048567813062, 694995078406056, 491336887915201185, 364377975224032162000, 280380150421755638519408, 222165159124597435189467696, 180288439972217748901049985158, 149230751849318301857448761484400, 125602423480863080624602495191566250
Offset: 0

Views

Author

Vaclav Kotesovec, Nov 23 2012

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Sum[Binomial[n+k,k]^5, {k,0,n}], {n,0,20}]

Formula

a(n) ~ 2^(10*n+5)/(31*(Pi*n)^(5/2)).

A219564 Sum(binomial(n+k,k)^6, k=0..n).

Original entry on oeis.org

1, 65, 47386, 65004097, 119498671876, 260128695981674, 632156164654144530, 1659900189891175027265, 4616088190888638302435080, 13418259230056806455830305940, 40401802613222456104862752944356, 125182282922559710456869140648653290, 397195659937314116991934285462527257236
Offset: 0

Views

Author

Vaclav Kotesovec, Nov 23 2012

Keywords

Crossrefs

Cf. A001700 (q=1), A112029 (q=2), A112028 (q=3), A219562 (q=4), A219563 (q=5).

Programs

  • Mathematica
    Table[Sum[Binomial[n+k,k]^6, {k,0,n}], {n,0,20}]

Formula

a(n) ~ 2^(12*n+6)/(63*Pi^3*n^3)
Generally (for q > 0), Sum_{k=0..n} C(n + k,k)^q is asymptotic to 2^((2*n+1)*q)/((2^q-1)*(Pi*n)^(q/2)) * (1 - q/(2*n)*(1/4+1/(2^q-1)^2) + O(1/n^2))

A295612 a(n) = Sum_{k=0..n} binomial(n+k,k)^k.

Original entry on oeis.org

1, 3, 40, 8105, 24053106, 1016507243472, 622366942086680904, 5608321882919220905812521, 752711651805019773658037206391596, 1518219710649896586598445898967340890577318, 46343146356260529633020448755386347142785083052620084
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 24 2017

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Sum[Binomial[n + k, k]^k, {k, 0, n}], {n, 0, 10}]
    Table[Sum[((n + k)!/(n! k!))^k, {k, 0, n}], {n, 0, 10}]
  • PARI
    a(n) = sum(k=0, n, binomial(n+k,k)^k); \\ Michel Marcus, Nov 25 2017

Formula

a(n) = Sum_{k=0..n} A046899(n,k)^k.
a(n) ~ 2^(2*n^2) / (exp(1/8) * Pi^(n/2) * n^(n/2)). - Vaclav Kotesovec, Nov 25 2017

A336829 a(n) = Sum_{k=0..n} binomial(n+k,k)^n.

Original entry on oeis.org

1, 3, 46, 9065, 25561876, 1048567813062, 632156164654144530, 5652307059542612442465921, 755658094192422806457805924637704, 1521188219372604726826961340683399629967888, 46388428590466766659538640978460161019178279424832676
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 05 2020

Keywords

Crossrefs

Programs

  • Magma
    [(&+[Binomial(2*n-j,n)^n: j in [0..n]]): n in [0..20]]; // G. C. Greubel, Aug 31 2022
    
  • Mathematica
    Table[Sum[Binomial[n + k, k]^n, {k, 0, n}], {n, 0, 10}]
  • PARI
    a(n) = sum(k=0, n, binomial(n+k, k)^n); \\ Michel Marcus, Aug 05 2020
    
  • SageMath
    def A336829(n): return sum(binomial(2*n-j, n)^n for j in (0..n))
    [A336829(n) for n in (0..20)] # G. C. Greubel, Aug 31 2022

Formula

a(n) ~ exp(-1/8) * 2^(2*n^2) / (Pi*n)^(n/2). - Vaclav Kotesovec, Jul 10 2021

A374676 a(n) = Sum_{k=0..n} binomial(n+k-1,n) * binomial(n+k,n)^2.

Original entry on oeis.org

1, 4, 117, 4416, 191025, 8959098, 443175257, 22764880288, 1202693106969, 64935435950760, 3567189106107044, 198746486074429164, 11203798260525398593, 637866038409406067394, 36624374381748740836905, 2118319467225018572438976, 123307986154526506959597225
Offset: 0

Views

Author

Seiichi Manyama, Jul 16 2024

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n, binomial(n+k-1, n)*binomial(n+k, n)^2);

Formula

a(n) = Sum_{k=0..n} (k/(n+k)) * binomial(n+k,k)^3 for n > 0.
Showing 1-8 of 8 results.