This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A135726 #24 Feb 25 2025 11:56:18
%S A135726 2,3,17,79,4188799,2504902399,254561089305599,13106744139423334399999,
%T A135726 8483004771271882804592639999,
%U A135726 706526001186582385898210420541078864497278132689882316799999999,353401447088718405944982176443380974931403135679741865504466985287679999999999
%N A135726 Primes of the form k!!! - 1 = A007661(k) - 1, k > 0.
%C A135726 Sequence A084438 gives the easier-to-read n-values.
%C A135726 All terms greater than a(3) seem to end in the digit 9, or many 9 digits. a(17) ends with 51 9 digits. - _Harvey P. Dale_, Nov 28 2019
%H A135726 Harvey P. Dale, <a href="/A135726/b135726.txt">Table of n, a(n) for n = 1..17</a>
%H A135726 Ken Davis, <a href="http://mfprimes.free-dc.org">Status of Search for Multifactorial Primes</a>.
%H A135726 Ken Davis, <a href="http://mfprimes.free-dc.org/mfdata/f03m.html">Results for n!3-1</a>.
%H A135726 ProthSearch.net (on web.archive.org), <a href="http://web.archive.org/web/20050220234200/http://www.prothsearch.net/n3minus.txt">n3minus.txt</a>.
%F A135726 a(n) = A007661(A084438(n)) - 1. - _Elmo R. Oliveira_, Feb 25 2025
%e A135726 a(4) = 79 = 8*5*2 - 1 = 8!!! - 1 is the 4th prime of that form.
%t A135726 Select[Table[Times@@Range[n,1,-3],{n,150}]-1,PrimeQ] (* _Harvey P. Dale_, Nov 28 2019 *)
%o A135726 (PARI)
%o A135726 A007661(n) = prod(i=1,(n-1)\3,n-=3,n+!n)
%o A135726 for(n=1,999,if(isprime(A007661(n)-1),print1(A007661(n)-1,",")))
%Y A135726 Cf. A007661, A037082, A037083, A084438.
%K A135726 nonn
%O A135726 1,1
%A A135726 _M. F. Hasler_, Nov 26 2007