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

1,1

Links

Table of n, a(n) for n=1..45.

Example

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

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 *)

Crossrefs

Cf. A002113, A046759.

Sequence in context: A117689 A178374 A179147 * A052084 A075546 A167733

Adjacent sequences: A047736 A047737 A047738 * A047740 A047741 A047742

Keyword

nonn,base

Author

Carlos Rivera

Extensions

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

Status

approved