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

0,2

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.

Links

Table of n, a(n) for n=0..9.

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 *)

Crossrefs

Cf. A007505, A066174, A110056, A292936.

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

Sequence in context: A246492 A059411 A126017 * A034468 A283075 A130668

Adjacent sequences: A292934 A292935 A292936 * A292938 A292939 A292940

Keyword

nonn,more

Author

Antti Karttunen, Sep 28 2017

Status

approved