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 1-1 of 1 results.

A385993 a(n) is the number of distinct values appearing an odd number of times among A002487(0), ..., A002487(n).

Original entry on oeis.org

1, 2, 1, 2, 3, 4, 3, 2, 1, 2, 3, 4, 5, 4, 3, 2, 3, 4, 5, 6, 7, 8, 7, 6, 5, 6, 7, 6, 5, 4, 3, 2, 1, 2, 3, 4, 5, 6, 7, 8, 9, 8, 9, 10, 9, 10, 9, 8, 9, 10, 11, 10, 11, 10, 9, 10, 9, 8, 7, 6, 5, 4, 3, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 11, 12, 11, 12, 13, 12, 13
Offset: 0

Views

Author

Rémy Sigrist, Jul 14 2025

Keywords

Examples

			Sequence begins:
  n   a(n)  A091948(n)
  --  ----  ----------
   0     1           1
   1     2           1
   2     1           2
   3     2           1
   4     3           3
   5     4           1
   6     3           2
   7     2           2
   8     1           4
   9     2           1
  10     3           3
  11     4           1
  12     5           3
		

Crossrefs

Programs

  • PARI
    \\ See Links section.

Formula

a(n) = - Sum_{k = 1, n} (-1)^A091948(k).
abs(a(n+1) - a(n)) = 1.
a(n) = 1 iff n = 0 or n belongs to A004171.
Showing 1-1 of 1 results.