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

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

0,2

Links

Rémy Sigrist, Table of n, a(n) for n = 0..8192

Rémy Sigrist, PARI program

Index entries for sequences related to Stern's sequences

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.

Example

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

Prog

(PARI) \\ See Links section.

Crossrefs

Cf. A002487, A004171, A091948, A385991.

Sequence in context: A144735 A304734 A375088 * A202275 A030307 A175792

Adjacent sequences: A385990 A385991 A385992 * A385994 A385995 A385996

Keyword

nonn

Author

Rémy Sigrist, Jul 14 2025

Status

approved