A245209 Nonprimes such that it takes exactly 4 iterations of reverse-and-add digits to generate a prime.

10031, 10040, 10190, 10231, 10390, 10441, 10480, 10541, 10721, 10921, 10970, 11021, 11030, 11180, 11221, 11380, 11431, 11470, 11531, 11711, 11911, 11960, 12020, 12170, 12370, 12460, 12521, 12701, 12901, 12950, 13010, 13160, 13201, 13360, 13450, 13511, 13601

Offset

0,1

Links

Table of n, a(n) for n=0..36.

Example

Reversing digits and adding starting with 11021 -> 23032 -> 46064 -> 92128 -> 174257 and 174257 is a prime while the prior numbers are not primes.

Mathematica

p4Q[n_] := Module[{lst = NestList[# + FromDigits[Reverse[IntegerDigits[#]]] &, n, 4]}, NoneTrue[Most[lst], PrimeQ] && PrimeQ[Last[lst]]]; Select[Range[100000], p4Q](* using NoneTrue function from Mathematica version 10 *)

Crossrefs

Cf. A245208, A245210.

Sequence in context: A210130 A213319 A241880 * A205822 A251136 A213318

Adjacent sequences: A245206 A245207 A245208 * A245210 A245211 A245212

Keyword

nonn,base

Author

Harvey P. Dale, Jul 13 2014

Status

approved