[seqfan] Re: Reversing A281684.

[cwwuieee]

f(11)=1388.
-------- Original message --------From: michel.marcus at free.fr Date: 3/4/21  10:34 AM  (GMT-05:00) To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu> Subject: [seqfan] Reversing A281684. Dear Seqfans A281684 is defined as: Least composite k such that the concatenation of n consecutive composites, starting from k, is a prime. It has a few small values: A281684(2)= 8; A281684(6)= 14; A281684(14)= 15; A281684(24)= 18; A281684(302)= 16. So is it possible to reverse it ? f(n) = least number k such that the concatenation of k composite numbers starting from the n-th composite is prime f(3) = 2 2nd composite : 8 ; 89 is prime f(5) = 646 f(7) = 6 7th composite : 14 ; 141516182021 is prime f(8) = 14 f(9) = 302 f(10) = 24 Is it possible to find f(1), f(2), f(4), f(6) that are the first missing values for f() ? Best MM --Seqfan Mailing list - http://list.seqfan.eu/