A138861 Primes of form 10^n + 21.

31, 1021, 1000000021, 100000000000000021, 10000000000000000000000000000000000000000000000000000021, 100000000000000000000000000000000000000000000000000000000000000000000000000021

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, May 16 2008

Keywords

• nonn

Comments

The next term has 134 digits. - Harvey P. Dale, Jan 15 2017

Crossrefs

Cf. A108050.

Programs

Mathematica

a={};Do[p=10^n+21;If[PrimeQ[p],AppendTo[a,p]],{n,0,10^2}];Print[a];
Join[{31},Select[Table[100FromDigits[PadRight[{1},n,0]]+21,{n,150}],PrimeQ]] (* Harvey P. Dale, Jan 15 2017 *)

PARI

for(n=1,1e3,if(ispseudoprime(t=10^n+21),print1(t", "))) \\ Charles R Greathouse IV, May 15 2013