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.

A341456 Let T be the set of sequences {t(k), k >= 0} such that for any k >= 3, t(k) = t(k-1) + t(k-2) + t(k-3); a(n) is the least possible value of t(0) + t(1) + t(2) for an element t of T containing n.

Original entry on oeis.org

0, 1, 1, 1, 1, 2, 1, 1, 2, 3, 2, 1, 2, 1, 2, 3, 3, 3, 2, 3, 1, 3, 2, 4, 1, 3, 2, 3, 4, 3, 5, 3, 4, 2, 4, 3, 4, 1, 4, 3, 2, 5, 4, 5, 1, 5, 3, 5, 2, 5, 3, 5, 4, 3, 6, 5, 6, 3, 6, 4, 3, 2, 6, 4, 3, 5, 4, 7, 1, 7, 4, 7, 3, 4, 2, 7, 5, 4, 6, 5, 4, 1, 8, 5, 4, 3, 5
Offset: 0

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Author

Rémy Sigrist, Feb 12 2021

Keywords

Comments

This sequence is a variant of A249783; here we consider tribonacci-like sequences, there Fibonacci like sequences. The scatterplots of these sequences both present polygonal shapes emerging from the origin.

Examples

			The first terms of the elements t of T such that t(0) + t(1) + t(2) <= 2 are:
  t(0)+t(1)+t(2)  t(0)  t(1)  t(2)  t(3)  t(4)  t(5)  t(6)  t(7)  t(8)  t(9)
  --------------  ----  ----  ----  ----  ----  ----  ----  ----  ----  ----
               0     0     0     0     0     0     0     0     0     0     0
               1     0     0     1     1     2     4     7    13    24    44
               1     0     1     0     1     2     3     6    11    20    37
               1     1     0     0     1     1     2     4     7    13    24
               2     0     0     2     2     4     8    14    26    48    88
               2     0     1     1     2     4     7    13    24    44    81
               2     0     2     0     2     4     6    12    22    40    74
               2     1     0     1     2     3     6    11    20    37    68
               2     1     1     0     2     3     5    10    18    33    61
               2     2     0     0     2     2     4     8    14    26    48
- so a(0) = 0,
     a(1) = a(2) = a(3) = a(4) = a(6) = a(7) = a(11) = 1,
     a(5) = = a(8) = a(10) = 2.
		

Crossrefs

Programs

  • PARI
    See Links section.

Formula

a(n) = 0 iff n = 0.
a(n) = 1 iff n belongs to A213816.
a(n) <= n.