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 1-3 of 3 results.

A059737 Lesser of the smallest pair of consecutive numbers divisible by an n-th power, but neither divisible by an (n+1)-st power.

Original entry on oeis.org

2, 44, 135, 80, 8991, 29888, 356480, 2316032, 14073344, 24151040, 326481920, 689278976, 11573190656, 76876660736, 314944159743, 2035980763136, 28996228218879, 55637069004800, 766556765683712, 1375916505694208, 19656708706009088, 129341461907898368, 2280241934368767, 787449981119234048
Offset: 0

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Author

Don Reble, May 25 2002

Keywords

Crossrefs

Extensions

More terms from Sean A. Irvine, Oct 06 2022

A045622 Convolution of A000108 (Catalan numbers) with A045543.

Original entry on oeis.org

1, 25, 362, 3973, 36646, 299530, 2238676, 15613741, 103054094, 650194974, 3950996556, 23257207714, 133217073276, 745218012084, 4083224828328, 21966983072637, 116268166691358, 606474982072982, 3122157367765788
Offset: 1

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Keywords

Comments

Also convolution of A045530 with A000984 (central binomial coefficients); also convolution of A045505 with A000302 (powers of 4).

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 40); Coefficients(R!( (1-Sqrt(1-4*x))/(2*(1-4*x)^6) )); // G. C. Greubel, Jan 13 2020
    
  • Maple
    seq(coeff(series((1-sqrt(1-4*x))/(2*(1-4*x)^6), x, n+1), x, n), n = 0..40); # G. C. Greubel, Jan 13 2020
  • Mathematica
    CoefficientList[Series[(1-Sqrt[1-4*x])/(2*x*(1-4*x)^6), {n,0,40}], x] (* G. C. Greubel, Jan 13 2020 *)
  • PARI
    my(x='x+O('x^40)); Vec((1-sqrt(1-4*x))/(2*(1-4*x)^6)) \\ G. C. Greubel, Jan 13 2020
    
  • Sage
    def A045622_list(prec):
        P. = PowerSeriesRing(ZZ, prec)
        return P( (1-sqrt(1-4*x))/(2*(1-4*x)^6) ).list()
    A045622_list(40) # G. C. Greubel, Jan 13 2020

Formula

a(n) = binomial(n+6, 5)*(4^(n+1) - A000984(n+6)/A000984(5))/2, A000984(n) = binomial(2*n, n).
G.f.: x*c(x)/(1-4*x)^6, where c(x) = g.f. for Catalan numbers.

A046658 Triangle related to A001700 and A000302 (powers of 4).

Original entry on oeis.org

1, 3, 1, 10, 7, 1, 35, 38, 11, 1, 126, 187, 82, 15, 1, 462, 874, 515, 142, 19, 1, 1716, 3958, 2934, 1083, 218, 23, 1, 6435, 17548, 15694, 7266, 1955, 310, 27, 1, 24310, 76627, 80324, 44758, 15086, 3195, 418, 31, 1, 92378, 330818, 397923, 259356, 105102, 27866, 4867, 542, 35, 1
Offset: 1

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Author

Keywords

Examples

			Triangle begins as:
      1;
      3,     1;
     10,     7,     1;
     35,    38,    11,     1;
    126,   187,    82,    15,     1;
    462,   874,   515,   142,    19,    1;
   1716,  3958,  2934,  1083,   218,   23,   1;
   6435, 17548, 15694,  7266,  1955,  310,  27,  1;
  24310, 76627, 80324, 44758, 15086, 3195, 418, 31, 1;
		

Crossrefs

Column sequences for m=1..6: A001700, A000531, A029887, A045724, A045492, A045530.
Row sums: A046885.
Cf. A000302.

Programs

  • Magma
    A046658:= func< n,k | Binomial(n,k)*(Binomial(n+1,2)*Catalan(n )/Catalan(k-1) -4^(n-k+1)*Binomial(k,2))/(n*(n-k+1)) >;
    [A046658(n,k): k in [1..n], n in [1..12]]; // G. C. Greubel, Jul 28 2024
    
  • Mathematica
    T[n_, k_]:= (1/2)*Binomial[n,k-1]*(Binomial[2*n,n]/Binomial[2*(k-1), k -1] - 4^(n-k+1)*(k-1)/n);
    Table[T[n, k], {n,12}, {k,n}]//Flatten (* G. C. Greubel, Jul 28 2024 *)
  • SageMath
    def A046658(n,k): return (1/2)*binomial(n,k-1)*(binomial(2*n, n)/binomial(2*(k-1), k-1) - 4^(n-k+1)*(k-1)/n)
    flatten([[A046658(n,k) for k in range(1,n+1)] for n in range(1,13)]) # G. C. Greubel, Jul 28 2024

Formula

T(n, k) = (1/2)*binomial(n, k-1)*( binomial(2*n, n)/binomial(2*(k-1), k-1) - 4^(n-k+1)*(k-1)/n ), n >= k >= 1.
G.f. for column k: x*c(x)*((x/(1-4*x))^(k-1))/sqrt(1-4*x), where c(x) is the g.f. for Catalan numbers (A000108).
Showing 1-3 of 3 results.