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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A059342 Triangle giving denominators of coefficients of Euler polynomials, highest powers first.

Original entry on oeis.org

1, 1, 2, 1, 1, 1, 1, 2, 1, 4, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 4, 1, 2, 1, 8, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 4, 1, 1, 1, 4, 1, 2, 1, 4, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2
Offset: 0

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Author

N. J. A. Sloane, Jan 27 2001

Keywords

Examples

			1; x-1/2; x^2-x; x^3-3*x^2/2+1/4; ...
		

References

  • M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 809.
  • L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 48, [14b].

Crossrefs

Programs

  • Maple
    for n from 0 to 30 do for k from n to 0 by -1 do printf(`%d,`,denom(coeff(euler(n,x), x, k))) od:od:
  • Mathematica
    Denominator[Table[Reverse[CoefficientList[Series[EulerE[n, x], {x, 0, 20}], x]], {n, 0, 10}]] (* G. C. Greubel, Jan 07 2017 *)

Extensions

More terms from James Sellers, Jan 29 2001

A215097 a(n) = n^3 - a(n-2) for n >= 2 and a(0)=0, a(1)=1.

Original entry on oeis.org

0, 1, 8, 26, 56, 99, 160, 244, 352, 485, 648, 846, 1080, 1351, 1664, 2024, 2432, 2889, 3400, 3970, 4600, 5291, 6048, 6876, 7776, 8749, 9800, 10934, 12152, 13455, 14848, 16336, 17920, 19601, 21384, 23274, 25272, 27379, 29600, 31940, 34400, 36981, 39688, 42526
Offset: 0

Views

Author

Alex Ratushnyak, Aug 03 2012

Keywords

Crossrefs

Cf. A000217 (n^2 - a(n-1)).
Cf. A125577 (n^2 - a(n-1) with a(0)=1).
Cf. A011934 (n^3 - a(n-1)).
Cf. A153026 (n^3 - a(n-1) with a(1)=0).
Cf. A194274 (n^2 - a(n-2)).
Cf. A187093 (n^2 - a(n-2) with a(0)=a(1)=1, a(-1)=0).
Cf. A107386 ((n-2)^2 - a(n-1) with a(0)=0, a(1)=a(2)=1, a(3)=2).
Cf. A206481 ((n-1)^3 - a(n-2)).

Programs

  • Mathematica
    RecurrenceTable[{a[0] == 0, a[1] == 1, a[n] == n^3 - a[n - 2]}, a[n], {n, 0, 43}] (* Bruno Berselli, Aug 07 2012 *)
  • Python
    prpr = 0
    prev = 1
    for n in range(2,77):
        print(prpr, end=',')
        curr = n*n*n - prpr
        prpr = prev
        prev = curr

Formula

G.f.: (x+4*x^2+x^3)/((-1+x)^4*(1+x^2)). - David Scambler, Aug 06 2012
a(n) = (n*(n^2-3)-(1-(-1)^n)*i^(n+1))/2, where i=sqrt(-1). - Bruno Berselli, Aug 07 2012

A382973 a(n) = 4*n^3 - 6*n^2 + 6*n - 2 + (-1)^n.

Original entry on oeis.org

1, 19, 69, 183, 377, 683, 1117, 1711, 2481, 3459, 4661, 6119, 7849, 9883, 12237, 14943, 18017, 21491, 25381, 29719, 34521, 39819, 45629, 51983, 58897, 66403, 74517, 83271, 92681, 102779, 113581, 125119, 137409, 150483, 164357, 179063, 194617, 211051, 228381, 246639
Offset: 1

Views

Author

Nicolay Avilov, Jun 02 2025

Keywords

Comments

a(n) is the number of 1 X 1 X 1 black cubes in a cube (2*n - 1) X (2*n - 1) X (2*n - 1), which is made up of 1 X 1 X 1 black cubes and 1 X 1 X 1 white cubes. In this case, any 1 X 1 X 1 cube is either completely black or completely white. The black and white cubes are arranged as follows: if the central cube has coordinates (0, 0, 0), then all cubes with coordinates (0, y, z), (x, 0, z) and (x, y, 0) are black. Then the cubes adjacent to the black ones are painted white so that a triangular layer with all white cubes is obtained. There will be eight such layers. In the next step, all cubes adjacent to the white ones are painted black so that a triangular layer of black cubes is formed, and so on, alternating layers of black cubes and layers of white cubes until all the cubes are painted (see the link "Illustration of coloring a cube").

Examples

			a(2) = 3^3 - 8*1 = 19;
a(3) = 5^3 - 8*7 = 69.
		

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{3, -2, -2, 3, -1}, {1, 19, 69, 183, 377}, 20] (* Hugo Pfoertner, Jun 12 2025 *)

Formula

a(n) = (2n - 1)^3 - 8*A011934(n-1).
G.f.: x*(1 + 16*x + 14*x^2 + 16*x^3 + x^4)/((1 - x)^4*(1 + x)). - Stefano Spezia, Jun 12 2025
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