|
%I #12 Jun 02 2023 15:02:19
%S 89,809,6569,65609,531521,538001,590489,4782977,4783697,47829689,
%T 3486784409,3491567369,3529831121,31768480097,34867844009,
%U 282430067921,285916320881,313810596089,2541865834889,22877179875449,25418658283289
%N Primes of the form m = 9^i + 9^j - 1, where i > j >= 0.
%C The base-9 representation of a term 9^i + 9^j - 1 has base-9 digital sum = 1 + 8*j == 1 (mod 8).
%C In base-9 representation the first terms are 108, 1088, 10008, 108888, 1000088, 1008888, 1088888, 10000008, 10000888, 108888888, 10000000008, 10008888888, 10088888888, 100888888888, ...
%H Hieronymus Fischer, <a href="/A239719/b239719.txt">Table of n, a(n) for n = 1..40</a>
%e a(1) = 89, since 89 = 9^2 + 9^1 - 1 is prime.
%e a(2) = 809, since 809 = 9^3 + 9^2 - 1 is prime.
%t Select[Flatten[Table[9^i+9^j-1,{i,0,20},{j,0,i-1}]],PrimeQ] (* _Harvey P. Dale_, Jun 02 2023 *)
%o (Smalltalk)
%o A239719
%o "Answer an array of the first n terms of A239719.
%o Uses method primesWhichAreDistinctPowersOf: b withOffset: d from A239712.
%o Usage: n A239719
%o Answer: #(89 809 ... ) [a(1) ... a(n)]"
%o ^self primesWhichAreDistinctPowersOf: 9 withOffset: -1
%K nonn
%O 1,1
%A _Hieronymus Fischer_, Apr 14 2014
|
