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.

A279636 Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the exponential transform of the k-th powers.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 3, 5, 1, 1, 5, 10, 15, 1, 1, 9, 22, 41, 52, 1, 1, 17, 52, 125, 196, 203, 1, 1, 33, 130, 413, 836, 1057, 877, 1, 1, 65, 340, 1445, 3916, 6277, 6322, 4140, 1, 1, 129, 922, 5261, 19676, 41077, 52396, 41393, 21147, 1, 1, 257, 2572, 19685, 104116, 288517, 481384, 479593, 293608, 115975
Offset: 0

Views

Author

Alois P. Heinz, Dec 16 2016

Keywords

Examples

			Square array A(n,k) begins:
:   1,    1,    1,     1,      1,       1,        1, ...
:   1,    1,    1,     1,      1,       1,        1, ...
:   2,    3,    5,     9,     17,      33,       65, ...
:   5,   10,   22,    52,    130,     340,      922, ...
:  15,   41,  125,   413,   1445,    5261,    19685, ...
:  52,  196,  836,  3916,  19676,  104116,   572036, ...
: 203, 1057, 6277, 41077, 288517, 2133397, 16379797, ...
		

Crossrefs

Rows n=0+1,2 give: A000012, A000051.
Main diagonal gives A279644.
Cf. A145460.

Programs

  • Maple
    egf:= k-> exp(exp(x)*add(Stirling2(k, j)*x^j, j=0..k)-`if`(k=0, 1, 0)):
    A:= (n, k)-> n!*coeff(series(egf(k), x, n+1), x, n):
    seq(seq(A(n, d-n), n=0..d), d=0..12);
    # second Maple program:
    A:= proc(n, k) option remember; `if`(n=0, 1,
          add(binomial(n-1, j-1)*j^k*A(n-j, k), j=1..n))
        end:
    seq(seq(A(n, d-n), n=0..d), d=0..12);
  • Mathematica
    A[n_, k_] := A[n, k] = If[n==0, 1, Sum[Binomial[n-1, j-1]*j^k*A[n-j, k], {j, 1, n}]]; Table[A[n, d-n], {d, 0, 12}, {n, 0, d}] // Flatten (* Jean-François Alcover, Feb 19 2017, translated from Maple *)

Formula

E.g.f. of column k: exp(exp(x)*(Sum_{j=0..k} Stirling2(n,j)*x^j) - delta_{0,k}).

A320939 a(n) = n! * [x^n] log(1 + Sum_{k>=1} k^n*x^k/k!).

Original entry on oeis.org

0, 1, 3, 5, -650, -46071, 3121776, 5538166381, 3146076001776, -10459815889305231, -100694615309371571840, -193538025548431984737219, 38912028315765820944424730112, 2554132880645627969533690819801657, -106074951996903194289368162206783509504
Offset: 0

Views

Author

Ilya Gutkovskiy, Oct 28 2018

Keywords

Comments

a(n) is the n-th term of the logarithmic transform of the n-th powers.

Crossrefs

Programs

  • Maple
    seq(coeff(series(factorial(n)*log(1+add(k^n*x^k/factorial(k),k=1..n)),x,n+1), x, n), n = 0 .. 15); # Muniru A Asiru, Oct 28 2018
  • Mathematica
    Table[n! SeriesCoefficient[Log[1 + Sum[k^n x^k/k!, {k, 1, n}]], {x, 0, n}], {n, 0, 14}]

A362384 Number of nonisomorphic magmas with n elements satisfying the equation x(yz) = xz.

Original entry on oeis.org

1, 1, 4, 12, 81, 934, 23703, 1219177
Offset: 0

Views

Author

Andrew Howroyd, Apr 24 2023

Keywords

Crossrefs

Cf. A001329 (magmas), A279644 (labeled case), A362385.

A320254 a(n) = n! * [x^n] exp(exp(x)*(x + (n/2 - 1)*x^2)).

Original entry on oeis.org

1, 1, 3, 16, 125, 1291, 16177, 241207, 4153193, 81082225, 1770989921, 42763506919, 1131353484637, 32541516492811, 1011058416700529, 33745374949198231, 1204107124715441873, 45741398365345761073, 1843069565594762478145, 78511973999963036415967, 3525468554804288803649381
Offset: 0

Views

Author

Ilya Gutkovskiy, Oct 08 2018

Keywords

Comments

For n > 2, a(n) is the n-th term of the exponential transform of n-gonal numbers.

Crossrefs

Programs

  • Mathematica
    Table[n! SeriesCoefficient[Exp[Exp[x] (x + (n/2 - 1) x^2)], {x, 0, n}], {n, 0, 20}]
Showing 1-4 of 4 results.