A349946 a(n) = A349526(n) + A349526(n+1).

2, 3, 4, 3, 4, 5, 5, 6, 4, 5, 6, 6, 7, 7, 8, 5, 6, 7, 7, 8, 8, 9, 9, 10, 6, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 7, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13, 14, 8, 9, 10, 10, 11, 11, 12, 12, 13, 13, 14, 14, 15, 15, 16, 9, 10, 11, 11, 12, 12, 13, 13, 14, 14, 15

Offset

1,1

Comments

Every positive integer n >= 2 occurs exactly n-1 times; the last occurrence of n is a((n-1)^2).

Links

Table of n, a(n) for n=1..74.

Example

A349426 = (1,1,2,2,1,3,2,3,3,1,4,2,4,3,4,4,1,...), in which every pair i,j of positive integers occurs exactly once; a(1) = 1+1, a(2) = 1+2, a(3) = 2+2.

Mathematica

t = {1, 1}; Do[t = Join[t, Riffle[Range[n], n], {n}], {n, 2, 100}];
u = Flatten[Partition[t, 2]];
v = Table[n (n + 1), {n, 1, 80}];
d = Delete[u, Map[{#} &, v]]; (* A349526 *)
p = Table[{d[[n]], d[[n + 1]]}, {n, 1, 150}];
Map[Total, p]  (* A349946 *)

Crossrefs

Cf. A349526, A349947 (array: row n shows positions of n+1 in A349946).

Sequence in context: A374054 A307531 A125619 * A262519 A225320 A308937

Adjacent sequences: A349943 A349944 A349945 * A349947 A349948 A349949

Keyword

nonn

Author

Clark Kimberling, Dec 07 2021

Status

approved