A349426 -id:A349426 - cp's OEIS frontend

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

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Clark Kimberling, Dec 07 2021

nonn

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

			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.

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

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 *)

cp's OEIS Frontend

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

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