A047739 Economical palindromes.

343, 1331, 10201, 14641, 31213, 94249, 1030301, 1332331, 1367631, 1478741, 2060602, 2513152, 2551552, 2570752, 2939392, 2977792, 3090903, 3498943, 3637363, 3735373, 3850583, 5221225, 5265625, 5734375, 6948496, 11288211, 11333311, 12100121, 12499421, 13577531, 14655641, 22666622, 27700772, 29399392, 31244213, 33999933, 38988983, 58344385, 71111117, 100020001, 100585001, 101000101, 104060401, 104555401, 106878601

Offset: 1

Author

Carlos Rivera

Keywords

• nonn
• base

Examples

			343 = 7^3; 3 digits in 343, 2 digits in 7^3, so 343 is economical.
		

Crossrefs

Cf. A002113, A046759.

Programs

Mathematica

d[n_]:=IntegerDigits[n]; palQ[n_]:=Reverse[(x=d[n])]==x; ecQ[n_]:=Length[Flatten[d[{First/@(x=FactorInteger[n]), DeleteCases[Last/@x,1]}]]] < Length[d[n]]; t={}; Do[If[palQ[n] && ecQ[n], AppendTo[t,n]], {n,3860000}]; t (* Jayanta Basu, May 16 2013 *)

Extensions

a(11)-a(45) from Donovan Johnson, Nov 24 2010