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.

A368609 a(n) = A368945(A071561(n)).

Original entry on oeis.org

0, 2, 4, 0, 8, 10, 2, 14, 16, 0, 6, 20, 8, 2, 26, 28, 4, 12, 34, 14, 6, 38, 40, 2, 18, 44, 10, 4, 50, 0, 12, 24, 56, 58, 26, 2, 64, 8, 16, 68, 70, 32, 4, 10, 0, 76, 36, 80, 6, 38, 22, 86, 14, 24, 42, 8, 94, 98, 4, 100, 0, 48, 104, 106, 30, 110, 6, 12, 20, 54, 2, 56, 34, 22, 14, 124, 36, 128, 4, 62
Offset: 1

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Author

Hartmut F. W. Hoft, Jan 25 2024

Keywords

Comments

This sequence lists all nonnegative numbers in A368945, all of which are even.
Conjecture: Every nonnegative even number occurs in this sequence.

Examples

			a(4) = A368945(A071561(4)) = A368945(10) = 0 and a(5) = A368945(A071561(5)) = A368945(11) = 8.
For numbers k <= 10^6 the largest width 0 extent instantiated is 999980 for prime 999983 and the smallest width 0 extent not instantiated by any k <= 10^6 is 31396.
		

Crossrefs

Programs

  • Mathematica
    a071561Q[n_] := Select[Divisors[n], Sqrt[n/2]<=#A249223 *)
    zeroExt[n_] := Module[{s=Position[t249223[n], 1][[-1, -1]]}, 2 Ceiling[(n+1)/(s+1)-(s+1)/2]-2]
    a368609[n_] := Map[zeroExt, Select[Range[n], a071561Q]]
    a368609[135]