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 A057034 #9 May 20 2022 08:31:49
%S A057034 3,2,5,2,5,4,7,4,7,4,23,2,19,2,97,2,19,64,17,62,19,4,17,58,23,64,157,
%T A057034 122,47,106,47,4,29,146,31,64,29,8,71,8,43,32,31,128,67,122,41,2,37,
%U A057034 146,137,122,191,142,59,128,71,284,109,274,101,218,97,32,83,158,53,166
%N A057034 Difference between n!! and the first prime before n!! - 1.
%C A057034 Analogous to the lesser Fortunate numbers but unlike them, all entries are not prime. Must odd entries are powers of two and all even entries are primes.
%t A057034 PrevPrime[ n_Integer ] := (k=n-1; While[ !PrimeQ[ k ], k-- ]; Return[ k ]); f[ n_Integer ] := (p = n!! - 1; q = PrevPrime[ p ]; Return[ p - q + 1 ]); Table[ f[ n ], {n, 4, 75} ]
%Y A057034 Cf. A006882, A057019.
%K A057034 nonn
%O A057034 4,1
%A A057034 _Robert G. Wilson v_, Sep 09 2000