# [seqfan] Re: My first base-10 related question here, I think

Jack Brennen jfb at brennen.net
Fri Jun 26 01:10:44 CEST 2009

```Note that the first "really big" member of the sequence is:

161 2179 2203 2207 ...  5923 5927 593

which has 1,818 digits.

Jack Brennen wrote:
> Leroy Quet wrote:
>> I usually loathe those base 10 sequences. But this sequence just isn't as interesting in base 2.
>>
>> Maybe this has been discussed here before. Probably, but I missed it then.
>>
>> Take all the primes written in base 10, and concatenate the list.
>>
>> 23571113171923293137...
>>
>> Next, starting on the left at the 2, place commas between the digits so that each comma is at the first place (the least amount of distance to the right) right of the last comma so that the digits in between the commas form primes.
>>
>> So we have the list of primes created:
>>
>> 2, 3, 5, 7, 11, 13, 17, 19,... (same as the original primes so far),
>> then  2, 3, 2, then what? (The next prime starts with a 931...)
>>
>
>
> 2
> 3
> 5
> 7
> 11
> 13
> 17
> 19
> 2
> 3
> 2
> 93137414347535961677173798389971011031071091131
> 2
> 7
> 13
> 11
> 3
> 7
> 13
> 91491511
> 5
> 7
> 163
> 167
> 17
> 3
> 17
> 9181
> 19
> 11
> 9319
> 7
> 19
> 9211223227229233239241251257
> 2
> 6326927
> 127
> 7
> 2
> 81283
> 2
> 93307
> 3
> 11
> 3
> 13
> 3
> 17
> 3
> 3
> 13
> 3
> 7
> 3
> 47
> 3
> 493533593673733
> 7
> 938338939
> 7
> 401
> 409
> 41
> 9421
> 43
> 1433
> 43
> 9443449457461
> 463
> 467
> 47
> 948749
> 149
> 9503509521523
> 5
> 41
> 5
> 47
> 5
> 5
> 7
> 5
> 6356957
> 157
> 7
> 5
> 87593599601607613617619631641
> 643
> 647
> 653
> 659
> 661
> 67
> 3
> 67
> 7
> 683
> 691
> 7
> 17
> 97
> 19
> 7
> 2
> 7
> 7
> 3
> 3
> 7
> 3
> 97
> 43
> 7
> 5
> 17
> 5
> 7
> 7
> 61
> 7
> 6977
> 3
> 7
> 877
> 97
> 809
> 811
> 821
> 823
> 827
> 829
> 83
> 9853857859863877881883887907911919929937941947953967971
> 97
> 7
> 983
> 991
> 997
>
>
>
>
> GP program to print out the list:
>
> a=0;
>
> tryd(d) =
> {
>    a=a*10+d;
>    if(isprime(a),print(a);a=0);
> }
>
> try(p) =
> {
>    if(p>=10,try(p\10));
>    tryd(p%10);
> }
>
> forprime(p=2,1000,try(p));
>
>
>
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>
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>
>

```