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

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, Oct 31 2002 *)

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.

Intersection of A002113 and A246547.

Sequence in context: A046450 A077271 A084093 * A076703 A360900 A305372

Adjacent sequences: A072034 A072035 A072036 * A072038 A072039 A072040

Keyword

nonn,base

Author

Labos Elemer, Jun 07 2002

Extensions

a(11)-a(12) from Klaus Brockhaus, Jun 07 2002

a(13)-a(16) from Robert G. Wilson v, Oct 31 2002

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

Status

approved