A292937 a(0)=1, followed by highly safe primes: positions of records in A292936.

1, 2, 5, 11, 23, 47, 2879, 71850239, 2444789759, 21981381119

Offset: 0

Author

Antti Karttunen, Sep 28 2017

Keywords

• nonn
• more

Comments

The starting offset is 0 to accommodate 1, which is only nonprime in this sequence, and also to align with the indexing used in A110056.

Sequence starts like A007505, and at least for terms a(5) .. a(9) is equal to A110056.

Crossrefs

Cf. A007505, A066174, A110056, A292936.

Cf. A000040, A005385, A066179, A157358, A157359 (each starts with the term a(1) .. a(5) of this sequence).

Programs

Mathematica

With[{s = Table[SelectFirst[Range[0, 10], ! PrimeQ@ Floor[n/(2^#)] &], {n, 10^7}]}, Map[FirstPosition[s, #][[1]] &, Union@ FoldList[Max, s]]] (* Michael De Vlieger, Sep 29 2017 *)