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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A374438 Triangle read by rows: T(n, k) = T(n - 1, k) + T(n - 2, k - 2), with initial values T(n, k) = k + 1 for k < 3.

Original entry on oeis.org

1, 1, 2, 1, 2, 3, 1, 2, 3, 2, 1, 2, 3, 4, 3, 1, 2, 3, 6, 6, 2, 1, 2, 3, 8, 9, 6, 3, 1, 2, 3, 10, 12, 12, 9, 2, 1, 2, 3, 12, 15, 20, 18, 8, 3, 1, 2, 3, 14, 18, 30, 30, 20, 12, 2, 1, 2, 3, 16, 21, 42, 45, 40, 30, 10, 3, 1, 2, 3, 18, 24, 56, 63, 70, 60, 30, 15, 2
Offset: 0

Views

Author

Peter Luschny, Jul 22 2024

Keywords

Comments

See A374439 and the cross-references for comments about this family of triangles, where the recurrence is defined as in the name, but with an additional parameter m for the initial values: T(n, k) = k + 1 for k < m.
As m -> oo, the rows of the triangles become the initial segments of the integers.

Examples

			Triangle starts:
  [ 0] [1]
  [ 1] [1, 2]
  [ 2] [1, 2, 3]
  [ 3] [1, 2, 3,  2]
  [ 4] [1, 2, 3,  4,  3]
  [ 5] [1, 2, 3,  6,  6,  2]
  [ 6] [1, 2, 3,  8,  9,  6,  3]
  [ 7] [1, 2, 3, 10, 12, 12,  9,  2]
  [ 8] [1, 2, 3, 12, 15, 20, 18,  8,  3]
  [ 9] [1, 2, 3, 14, 18, 30, 30, 20, 12,  2]
  [10] [1, 2, 3, 16, 21, 42, 45, 40, 30, 10, 3]
		

Crossrefs

Family of triangles: A162515 (m=1, Fibonacci), A374439 (m=2, Lucas), this triangle (m=3).
Row sums: A187890 (apart from initial terms), also A001060 + 1 (with 1 prepended).
Cf. A006355 (odd sums), A187893 (even sums).
Cf. related to deltas: A065220, A210673.

Programs

  • Maple
    M := 3;  # family index
    T := proc(n, k) option remember; if k > n then 0 elif k < M then k + 1 else
    T(n - 1, k) + T(n - 2, k - 2) fi end:
    seq(seq(T(n, k), k = 0..n), n = 0..11);
  • Python
    from functools import cache
    @cache
    def T(n: int, k: int) -> int:
        if k > n: return 0
        if k < 3: return k + 1
        return T(n - 1, k) + T(n - 2, k - 2)

A224824 Smallest m such that Fibonacci(m) >= m^n.

Original entry on oeis.org

5, 12, 21, 30, 41, 51, 62, 73, 85, 97, 109, 122, 134, 147, 160, 174, 187, 200, 214, 228, 242, 256, 270, 284, 298, 312, 327, 342, 356, 371, 386, 401, 416, 431, 446, 461, 476, 491, 507, 522, 538, 553, 569, 585, 600, 616, 632, 648, 664, 680
Offset: 1

Views

Author

Michel Marcus, Jul 21 2013

Keywords

Crossrefs

Programs

  • Mathematica
    Flatten[{5,Table[Ceiling[(n*LambertW[-1,-Log[GoldenRatio]/(n*5^(1/(2*n)))])/-Log[GoldenRatio]],{n,2,50}]}] (* Vaclav Kotesovec, Jul 24 2013 *)
  • PARI
    a(n) = {my(ok = 0, m = 2); until (ok, if (fibonacci(m) >= m^n, ok = 1, m++); ); return (m); } \\ Michel Marcus, Jul 21 2013; corrected Jun 13 2022

A340326 a(n) = a(n-2) + (-1)^n*a(n-1) + n*(1-(-1)^n) with a(0) = a(1) = 1.

Original entry on oeis.org

1, 1, 2, 5, 7, 8, 15, 7, 22, 3, 25, 0, 25, 1, 26, 5, 31, 8, 39, 7, 46, 3, 49, 0, 49, 1, 50, 5, 55, 8, 63, 7, 70, 3, 73, 0, 73, 1, 74, 5, 79, 8, 87, 7, 94, 3, 97, 0, 97, 1, 98, 5, 103, 8, 111, 7, 118, 3, 121, 0, 121, 1, 122, 5, 127, 8, 135, 7, 142, 3, 145, 0, 145, 1, 146, 5, 151
Offset: 0

Views

Author

Keywords

Comments

If n > 0 then a(2n-1) = A021067(n).
a(n) = 0 if and only if n == -1 (mod 12).

Crossrefs

Programs

  • Mathematica
    a[0] = 1; a[1] = 1; a[n_] := a[n] =  a[n - 2] + (-1)^n a[n - 1] + n (1 - (-1)^n); Array[a,100]

Formula

G.f.: -(x^6+3*x^5-5*x^4-2*x^3+x^2-x-1)/(x^8-3*x^6+4*x^4-3*x^2+1). - Alois P. Heinz, Feb 07 2021
Previous Showing 11-13 of 13 results.