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

1,1

Links

Table of n, a(n) for n=1..19.

Example

E.g. 94249=307*307

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)

Prog

(PARI) {a=10^15; v=[]; m=sqrt(a); forprime(p=2, m, q=p; while((q=q*p)<a, n=q; rev=0; while(n>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], ", "))}

Crossrefs

Cf. A025475, A002385.

Sequence in context: A046450 A077271 A084093 * A076703 A360900 A305372

Adjacent sequences: A072034 A072035 A072036 * A072038 A072039 A072040

Keyword

base,easy,nonn

Author

Labos Elemer, Jun 07 2002

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

Status

approved