A308721 Locations of the first occurrence of pair (0,n) in the van Eck sequence (A181391).

0, 1, 3, 20, 24, 10, 30, 276, 388, 81, 225, 726, 2935, 1408, 7718, 5624, 5680, 85998, 26706, 546290, 1112929, 702575, 3425417, 10537360, 21301906, 217230900, 108698091, 32381774, 846522986, 851764846, 11692311325, 46163898987

Offset: 0

Author

Tomas Rokicki, Jun 19 2019

Keywords

• sign
• more

Comments

a(33) = 118456929919 and a(34) = 250327022558 but we do not yet know a(32).

Examples

			For a(5)=10, the pair (0,5) first occurs in A181391 at element 10.
		

Crossrefs

Cf. A181391.

Programs

Mathematica

With[{s = Nest[# /. {{Longest[p___], a_, q___, a_} :> {p, a, q, a, Length[{a, q}]}, {a___} :> {a, 0}} &, {}, 10^3]}, TakeWhile[#, # > -1 &] &@ Array[If[Length@ # == 0, -1, #[[1, 1]] - 1 ] &@ SequencePosition[s, {0, #}] &, Max@ s, 0]] (* Michael De Vlieger, Jul 08 2019, after JungHwan Min at A181391 *)