A109627 Numbers n such that concatenation of n and its 10's complement is a palindromic prime.

91, 9091, 9271, 9451, 900991, 907291, 914581, 917281, 920971, 931861, 939061, 943651, 954541, 958141, 960931, 972721, 975421, 977221, 978121, 982711, 90027991, 90209791, 90272791, 90372691, 90381691, 90627391, 90745291

Offset

1,1

Comments

The Mathematica code can be modified to verify that the included list is a complete listing of the sequence such that a(n) < 100000000. - Keith Schneider (schneidk(AT)unc.edu), May 20 2007, May 21 2007

Links

Keith Schneider (schneidk(AT)unc.edu), May 20 2007, Table of n, a(n) for n = 1..108

Example

a(3)=9271 because 10^4-9271 = 729 and concatenating produces the palprime 9271729.

Mathematica

Mathematica code from Keith Schneider, May 21 2007:
Remove[PalList, PrimeList, SeqList]
PalList[n_] := PalList[n] = Table[FromDigits[Join[Join[{9},
PadLeft[IntegerDigits[i], n/2 - 1], Reverse[ PadLeft[IntegerDigits[ 10^(n/2 - 1) - 1 - i], n/2 - 1]], {1}], Reverse[Join[{9}, PadLeft[IntegerDigits[i], n/2 - 1], Reverse[ PadLeft[IntegerDigits[10^(n/2 - 1) - 1 - i], n/2 - 1]]]]]], { i, 0, 10^(n/2 - 1) - 10^(n/2 - 2) - 1}];
PrimeList[n_] := PrimeList[n] = Delete[Union[Table[If[ PrimeQ[PalList[n][[ i]]], PalList[n][[i]]], {i, 1, Length[PalList[n]]}]], -1];
SeqList[2] = {91};
SeqList[n_] := SeqList[n] = Table[FromDigits[IntegerDigits[ PrimeList[n][[i]]][[Range[n]]]], {i, 1, Length[PrimeList[n]]}];
TheList = Join[SeqList[2], SeqList[4], SeqList[6], SeqList[8],
SeqList[10], SeqList[12], SeqList[14]]; TheList // TableForm
Length[TheList]

Crossrefs

Sequence in context: A202564 A006244 A054216 * A095372 A165154 A015261

Adjacent sequences: A109624 A109625 A109626 * A109628 A109629 A109630

Keyword

base,nonn

Author

Jason Earls, Aug 02 2005

Extensions

More terms from Keith Schneider (schneidk(AT)unc.edu), May 20 2007, May 21 2007

Status

approved