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

Hans Havermann pxp at rogers.com
Fri Jun 26 20:49:17 CEST 2009

> could someone please send in a correction to A074721, and a b-file  
> for it?

Bob: The current comment prior to the "Problem: least k>9 with  
a(k)=A000040(k)?" can probably be deleted, as can the link that  
supports that part of the comment. A particular method of  
factorization is not really pertinent to the sequence.

I just want to bring up something that is not necessarily a problem  
for this sequence but I'd like someone's opinion on it regardless.  
When the primes 691, 701, 709, and 719 get concatenated and digitized,  
we end up with: {..., 6, 9, 1, 7, 0, 1, 7, 0, 9, 7, 1, 9, ...}. These  
will end up in A074721 as terms #98 - #102: {691, 7, 17, 97, 19}.  
Terms #100 & #101 have associated with them *unstated* leading zeros.  
This makes it difficult to construct the concatenated primes from just  
the sequence terms. Perhaps a comment to that effect might alert the  
unwary. The alternative would be to complicate the definition of the  
sequence to exclude leading zeros from existing, not the best solution.

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