A239716 Primes of the form m = 6^i + 6^j - 1, where i > j >= 0.

41, 251, 1301, 1511, 46691, 47951, 279941, 1679831, 10077911, 10124351, 60466181, 60466391, 60473951, 362797091, 362797271, 362843711, 2176782371, 2237248511, 13060694051, 13121160191, 78364164101, 78364164311, 78364171871

Offset: 1

Author

Hieronymus Fischer, Apr 14 2014

Keywords

• nonn

Comments

The base-6 representation of a term 6^i + 6^j - 1 has base-6 digital sum = 1 + 5*j == 1 (mod 5).

In base-6 representation the first terms are 105, 1055, 10005, 10555, 1000055, 1005555, 10000005, 100000555, 1000000555, 1000555555, 10000000005, 10000000555,

Examples

			a(1) = 41, since 41 = 6^2 + 6^1 - 1 is prime.
a(2) = 251, since 251 = 6^3 + 6^2 - 1 is prime.
		

Links

• Hieronymus Fischer, Table of n, a(n) for n = 1..60

Programs

Mathematica

Select[Union[Flatten[Table[6^i+6^j-1,{i,20},{j,0,i-1}]]],PrimeQ] (* Harvey P. Dale, Oct 05 2024 *)

Smalltalk

A239716
  "Answers an array of the first n terms of A239716.
  Uses method primesWhichAreDistinctPowersOf: b withOffset: d from A239712.
  Usage: n A239716
  Answer: #(41 241 ... ) [a(1) ... a(n)]"
  ^self primesWhichAreDistinctPowersOf: 6 withOffset: -1