A242846 Palindromic primes of the form ababa...aba containing only the digits 1 and 3.

131, 313, 1313131313131313131313131, 313131313131313131313131313131313131313131313131313

Offset: 1

Author

Felix Fröhlich, May 23 2014

Keywords

• nonn
• base

Comments

The next two terms both start with 3 and have 83 and 225 digits, respectively. Those are the only other terms with fewer than 352 digits. Cf. A062216.

Crossrefs

Cf. A062216, A032758, A048399, A235154.

Programs

Mathematica

Module[{nn=60,a,b},a=Table[FromDigits[Join[PadRight[{},2n,{1,3}],{1}]],{n,nn}];b=Table[FromDigits[Join[PadRight[{},2n,{3,1}],{3}]],{n,nn}];Select[Sort[Join[a,b]],PrimeQ]] (* Harvey P. Dale, Sep 07 2020 *)