A072037 Palindromic powers (with positive exponents) of a prime but not a prime (A025475).

4, 8, 9, 121, 343, 1331, 10201, 14641, 94249, 1030301, 104060401, 900075181570009, 10022212521222001, 12124434743442121, 12323244744232321, 12341234943214321, 1022321210249420121232201, 1210024420147410244200121, 1210222232227222322220121

Offset: 1

Author

Labos Elemer, Jun 07 2002

Keywords

• base
• easy
• nonn

Examples

			E.g. 94249=307*307
		

Crossrefs

Cf. A025475, A002385.

Programs

Mathematica

a = {}; Do[pp = Prime[n]^i; d = IntegerDigits[pp]; If[d == Reverse[d], a = Append[a, pp]], {n, 1, PrimePi[ Sqrt[10^21]]}, {i, 2, Floor[ Log[ Prime[n], 10^21]]}]; Sort[a] (Robert G. Wilson v)

PARI

{a=10^15; v=[]; m=sqrt(a); forprime(p=2,m,q=p; while((q=q*p)0,d=divrem(n,10); n=d[1]; rev=10*rev+d[2]); if(q==rev,v=concat(v,q)))); v=vecsort(v); for(j=1,matsize(v)[2],print1(v[j],","))}

Extensions

Two more term from Klaus Brockhaus, Jun 07 2002

Four more terms from Robert G. Wilson v, Oct 31 2002

Added a(17)-a(19), clarified definition, Donovan Johnson, Sep 01 2012