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 1-4 of 4 results.

A367011 a(n) = Sum_{k=0..n} k! * k^(n-k).

Original entry on oeis.org

1, 1, 3, 11, 51, 287, 1899, 14447, 124251, 1192127, 12623979, 146250287, 1840024251, 24983863967, 364140992139, 5670546353807, 93960923507931, 1650688221777407, 30646388716777899, 599565840087487727, 12328458398407260411
Offset: 0

Views

Author

Vaclav Kotesovec, Nov 01 2023

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Sum[k! * k^(n-k), {k, 0, n}], {n, 1, 20}]
  • PARI
    a(n) = sum(k=0, n, k!*k^(n-k)); \\ Seiichi Manyama, Dec 31 2023

Formula

a(n) ~ Pi * n^(n+1) / exp(n).
a(n) ~ sqrt(Pi*n/2) * n!.

Extensions

a(0)=1 prepended by Seiichi Manyama, Dec 31 2023

A350149 Triangle read by rows: T(n, k) = n^(n-k)*k!.

Original entry on oeis.org

1, 1, 1, 4, 2, 2, 27, 9, 6, 6, 256, 64, 32, 24, 24, 3125, 625, 250, 150, 120, 120, 46656, 7776, 2592, 1296, 864, 720, 720, 823543, 117649, 33614, 14406, 8232, 5880, 5040, 5040, 16777216, 2097152, 524288, 196608, 98304, 61440, 46080, 40320, 40320
Offset: 0

Views

Author

Robert B Fowler, Dec 27 2021

Keywords

Comments

T(n,k) are the denominators in a double summation power series for the definite integral of x^x. First expand x^x = exp(x*log(x)) = Sum_{n>=0} (x*log(x))^n/n!, then integrate each of the terms to get the double summation for F(x) = Integral_{t=0..x} t^t = Sum_{n>=1} (Sum_{k=0..n-1} (-1)^(n+k+1)*x^n*(log(x))^k/T(n,k)).
This is a definite integral, because lim {x->0} F(x) = 0.
The value of F(1) = 0.78343... = A083648 is known humorously as the Sophomore's Dream (see Borwein et al.).

Examples

			Triangle T(n,k) begins:
--------------------------------------------------------------------------
n/k         0        1       2       3      4      5      6      7      8
--------------------------------------------------------------------------
0  |        1,
1  |        1,       1,
2  |        4,       2,      2,
3  |       27,       9,      6,      6,
4  |      256,      64,     32,     24,    24,
5  |     3125,     625,    250,    150,   120,   120,
6  |    46656,    7776,   2592,   1296,   864,   720,   720,
7  |   823543,  117649,  33614,  14406,  8232,  5880,  5040,  5040,
8  | 16777216, 2097152, 524288, 196608, 98304, 61440, 46080, 40320, 40320.
...
		

References

  • Borwein, J., Bailey, D. and Girgensohn, R., Experimentation in Mathematics: Computational Paths to Discovery, A. K. Peters 2004.
  • William Dunham, The Calculus Gallery, Masterpieces from Newton to Lebesgue, Princeton University Press, Princeton NJ 2005.

Crossrefs

Cf. A000312 (first column), A000169 (2nd column), A003308 (3rd column excluding first term), A000142 (main diagonal), A000142 (2nd diagonal excluding first term), A112541 (row sums).
Values of the integral: A083648, A073009.

Programs

  • Magma
    A350149:= func< n,k | n^(n-k)*Factorial(k) >;
    [A350149(n,k): k in [0..n], n in [0..12]]; // G. C. Greubel, Jul 31 2022
    
  • Maple
    T := (n, k) -> n^(n - k)*k!:
    seq(seq(T(n, k), k = 0..n), n = 0..9); # Peter Luschny, Jan 07 2022
  • Mathematica
    T[n_, k_]:= n^(n-k)*k!; Table[T[n, k], {n, 0,12}, {k,0,n}]//Flatten (* Amiram Eldar, Dec 27 2021 *)
  • SageMath
    def A350149(n,k): return n^(n-k)*factorial(k)
    flatten([[A350149(n,k) for k in (0..n)] for n in (0..12)]) # G. C. Greubel, Jul 31 2022

Formula

T(n, 0) = A000312(n).
T(n, 1) = A000169(n).
T(n, 2) = A003308(n), n >= 2.
Sum_{k=0..n} T(n, k) = A112541(n).
T(n, n) = A000142(n).
T(n, n-1) = A000142(n), n >= 1.
T(n,k) = A061711(n) * (n+1) / A350297(n+1,k). - Robert B Fowler, Jan 11 2022

A368561 a(n) = Sum_{k=0..n} k! * n^k.

Original entry on oeis.org

1, 2, 11, 184, 6565, 390806, 34557919, 4237440628, 687219772553, 142347286888210, 36654963132246211, 11483715014356017104, 4300711472638444724653, 1897241450053063830832078, 973695564434830963964311655
Offset: 0

Views

Author

Seiichi Manyama, Dec 30 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n, k!*n^k);

Formula

a(n) ~ n! * n^n. - Vaclav Kotesovec, Jan 13 2024

A368555 a(n) = Sum_{k=0..n} k! * 3^(n-k).

Original entry on oeis.org

1, 4, 14, 48, 168, 624, 2592, 12816, 78768, 599184, 5426352, 56195856, 647589168, 8169788304, 111687656112, 1642737336336, 25851001897008, 433240433787024, 7702095007089072, 144751385430099216, 2867156164466937648, 59692410665110252944
Offset: 0

Views

Author

Seiichi Manyama, Dec 29 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n, k!*3^(n-k));

Formula

a(0) = 1; a(n) = 3*a(n-1) + n!.
a(n) = (n+3)*a(n-1) - 3*n*a(n-2).
a(n) ~ n!. - Vaclav Kotesovec, Jan 13 2024
Showing 1-4 of 4 results.