

A200065


Start with n, concatenate its trivial divisors, and repeat until a prime is reached. a(n) = 0 if no prime is ever reached.


1



0, 0, 13, 0, 0, 0, 17, 0, 19, 0, 1111111111111111111, 0, 113, 0, 0, 0, 1117, 0, 11119, 0, 111121, 0, 1123, 0, 0, 0, 127, 0, 1129, 0, 131, 0
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OFFSET

1,3


COMMENTS

a(33) has 715 digits and is too large to include.
a(A065502(n)) = 0. There are other integers for which a(n) = 0 (i.e., n = 221).
The number (10^270343  1)/9 appears 161046 times in this sequence.
All odd primes from A096497 are in the sequence.


LINKS



EXAMPLE

17 > {1, 17} = 117 (composite) > {1, 117} = 1117 (prime), so a(17) = 1117.


MATHEMATICA

lst = {}; Do[If[DivisorSigma[0, n] == 1  Divisible[n, 5]  EvenQ[n], AppendTo[lst, 0], If[PrimeQ[n], n = 10^Length[IntegerDigits[n]] + n]; While[True, If[PrimeQ[n], Break[]]; n = FromDigits[Flatten[IntegerDigits[{1, n}]]]]; AppendTo[lst, n]], {n, 32}]; lst


CROSSREFS



KEYWORD

base,nonn


AUTHOR



STATUS

approved



