A245210 Nonprimes such that it takes exactly 5 iterations of reverse-and-add digits to generate a prime.

1001320, 1001720, 1002220, 1004420, 1005520, 1005710, 1005910, 1006120, 1007420, 1008710, 1009220, 1009510, 1009610, 1011220, 1011620, 1012120, 1014320, 1015420, 1015610, 1015810, 1016020, 1017320, 1018610, 1019120, 1019410, 1019510, 1021120, 1021520

Offset

0,1

Links

Table of n, a(n) for n=0..27.

Example

Reversing and adding starting with 1005710 -> 1180711 -> 2351522 -> 4603054 -> 9106118 -> 17222137 and 17222137 is prime while the prior numbers are not primes.

Mathematica

p5Q[n_]:=Module[{lst=NestList[#+FromDigits[Reverse[ IntegerDigits[#]]]&, n, 5]}, NoneTrue[Most[lst], PrimeQ]&&PrimeQ[Last[lst]]]; Select[ Range[ 3000000], p5Q] (* using NoneTrue function from Mathematica version 10 *)

Crossrefs

Cf. A245208, A245209

Sequence in context: A227137 A096212 A065325 * A357098 A250698 A250683

Adjacent sequences: A245207 A245208 A245209 * A245211 A245212 A245213

Keyword

nonn,base

Author

Harvey P. Dale, Jul 13 2014

Status

approved