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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 (list; graph; refs; listen; history; text; internal format)
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

Arkadiusz Wesolowski, Table of n, a(n) for n = 1..1032

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

Cf. A004022, A096497.

Sequence in context: A127708 A094896 A277118 * A067155 A277255 A255288

Adjacent sequences:  A200062 A200063 A200064 * A200066 A200067 A200068

KEYWORD

base,nonn

AUTHOR

Arkadiusz Wesolowski, Apr 18 2012

STATUS

approved

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Last modified February 18 04:48 EST 2020. Contains 332011 sequences. (Running on oeis4.)