A115685 Prime numbers whose digit reversal is a powerful(1) number (A001694).

23, 61, 163, 293, 487, 521, 691, 821, 1297, 1861, 2531, 2731, 4201, 4441, 4483, 5209, 5227, 8429, 8867, 9049, 9631, 12391, 14437, 16141, 16987, 25153, 25703, 29741, 52163, 61483, 63211, 65579, 65707, 65899, 67057, 67901, 69481, 80687

Offset

1,1

Links

Chai Wah Wu, Table of n, a(n) for n = 1..8201 (terms 1..458 from Robert Israel)

Example

8867 is prime and 7688 = 2^3 * 31^2.

Maple

N:= 10000; # to get all entries <= N
F:= proc(p)
     local L, i, q, f;
     if not isprime(p) then return false end if;
     L:= convert(p, base, 10);
     q:= add(10^(i-1)*L[-i], i=1..nops(L));
     f:= ifactors(q)[2];
     not has(map2(op, 2, f), 1);
    end proc;
select(F, [2*i+1 $ i=1..floor((N-1)/2)]);
# Robert Israel, Feb 11 2013

Mathematica

fQ[n_] := Min[ Last@# & /@ FactorInteger@ FromDigits@ Reverse@ IntegerDigits@ n] > 1; Select[ Prime@ Range@ 8000, fQ] (* Robert G. Wilson v, Feb 11 2013 *)

Crossrefs

Cf. A001694.

Sequence in context: A031342 A215166 A141870 * A069798 A067194 A355984

Adjacent sequences: A115682 A115683 A115684 * A115686 A115687 A115688

Keyword

nonn,base

Author

Giovanni Resta, Jan 31 2006

Status

approved