A098980 Duplicate of A007647.
1, 3, 9, 21, 363, 2161, 4839, 49521, 105994
Offset: 1
This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
[n: n in [0..1500] | IsPrime(n*6^n+1)];
Select[Range[1500], PrimeQ[# 6^# + 1] &]
is(n)=ispseudoprime(n*6^n+1) \\ Charles R Greathouse IV, Feb 17 2017
lst={}; Do[ p=n*10^n+ 1; If[PrimeQ[p], AppendTo[lst, p]], {n, 0, 21}]; lst
Select[Table[n*10^n+1,{n,40}],PrimeQ] (* Harvey P. Dale, Jul 18 2020 *)
a(1) = 2 because 2 * 10^2 + 1 = 201 = 3 * 67. a(2) = 5 because 5 * 10^5 + 1 = 500001 = 3 * 166667. a(3) = 13 because 13*10^13 + 1 = 130000000000001 = 6529 * 19911165569. a(4) = 28 because 28 * 10^28 + 1 = 29 * 9655172413793103448275862069.
IsSemiprime:=func; [n: n in [1..70] | IsSemiprime(s) where s is n*10^n+1]; // Vincenzo Librandi, May 10 2014
Select[Range[40], PrimeOmega[# 10^# + 1] == 2 &] (* Alonso del Arte, Sep 08 2012 *)
[n: n in [0..100000] | IsPrime(n*9^n+1)];
Select[Range[100000], PrimeQ[# 9^# + 1] &]
for(n=1,100000, if(isprime(n*9^n+1), print1(n,", ")))
[n: n in [1..10000] |IsPrime(n*20^n+1)]
Select[Range[1, 10000], PrimeQ[n*20^n+1] &]
for(n=1, 10000, if(isprime(n*20^n+1), print1(n, ", ")))
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