A127959 Nonprime numbers of the form 1 + Sum_{k=1..m} 2^(2*k - 1).

171, 10923, 699051, 11184811, 44739243, 178956971, 2863311531, 11453246123, 45812984491, 183251937963, 733007751851, 11728124029611, 46912496118443, 187649984473771, 750599937895083, 3002399751580331, 12009599006321323

Offset

1,1

Comments

Prime numbers of the form 1 + Sum_{k=1..m} 2^(2*n - 1) is A000979. Numbers x such that 1 + Sum_{k=1..m} 2^(2*n - 1) is prime for n=1,2,...,x is A127936. A127955 is probably a subset of the present sequence.

Links

Table of n, a(n) for n=1..17.

Mathematica

a = {}; Do[c = 1 + Sum[2^(2n - 1), {n, 1, x}]; If[PrimeQ[c] == False, AppendTo[a, c]], {x, 1, 50}]; a
Select[Table[Sum[2^(2k-1), {k, n}]+1, {n, 50}], !PrimeQ[#]&] (* Harvey P. Dale, Dec 23 2017 *)

Crossrefs

Cf. A000979, A000978, A124400, A126614, A127955, A127956, A127957, A127958, A127936.

Sequence in context: A239270 A262142 A206595 * A046166 A262113 A145625

Adjacent sequences: A127956 A127957 A127958 * A127960 A127961 A127962

Keyword

nonn

Author

Artur Jasinski, Feb 09 2007

Status

approved