A379802 Indices k such that A377091(k) is immediately followed by A377091(k+1) = -A377091(k).

2, 12, 31, 60, 90, 132, 183, 241, 307, 380, 462, 552, 677, 997, 1125, 1444, 1563, 1722, 1892, 2117, 2257, 2450, 2652, 2914, 3081, 3306, 3540, 3782, 4033, 4291, 4560, 4830, 5112, 5403, 5701, 6006, 6320, 6643, 6972, 7311, 7657, 8464, 8743, 9121, 9506, 9902, 11238, 12100, 12542, 12883, 15877, 16257, 17424, 17823, 18361, 18906, 19462

Offset

1,1

Links

Rémy Sigrist, Table of n, a(n) for n = 1..10000 (first 209 terms from N. J. A. Sloane)

Rémy Sigrist, C++ program

Example

Terms 0 through 14 of A377091 are 0, 1, 2, -2, -1, 3, 4, 5, -4, -3, 6, 7, 8, -8, -7, and the pairs 2, -2 and 8, -8  correspond to a(1) = 2 and a(2) = 12.

Mathematica

(* A377091list is defined at A377091 *)
PositionIndex[Differences[Abs[A377091list[10000]]]][0] - 1 (* Paolo Xausa, Jan 22 2025 *)

Prog

(C++) // See Links section.

Crossrefs

Cf. A377091, A379066, A379788-A379794, A379803, A379804, A380837.

Sequence in context: A085892 A101177 A117625 * A297763 A254962 A139323

Adjacent sequences: A379799 A379800 A379801 * A379803 A379804 A379805

Keyword

nonn

Author

N. J. A. Sloane, Jan 19 2025

Status

approved