OFFSET
1,2
COMMENTS
Where records occur in A305382.
MATHEMATICA
With[{s = Array[Length@ NestWhile[Union@ Join[#, First /@ Flatten[FactorInteger[2 # + 1], 1]] &, {Prime@ #}, UnsameQ, All] &, 10^5]}, Map[FirstPosition[s, #][[1]] &, Union@ FoldList[Max, s] ] ] (* Michael De Vlieger, Jul 06 2018, after Robert G. Wilson v at A305382 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Hans Havermann, Jun 17 2018
STATUS
approved