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 A374621 #9 Jul 15 2024 10:20:24
%S A374621 1,1,1,2,5,24,120,720,5040,40320,362880,3628800,39916800,479001600,
%T A374621 6227020800,87178291200,1307674368000,20922789888000,355687428096000,
%U A374621 6402373705728000,121645100408832000,2432902008176640000,51090942171709440000,1124000727777607680000,25852016738884976640000
%N A374621 Expansion of e.g.f. 1 - x^4/24 - log(1 - x).
%C A374621 Conjectures (confirmed up to n = 10): (Start)
%C A374621 a(n) is the number of distinct values of the permanent of an n X n symmetric Toeplitz matrix having 0 on the main diagonal and all the integers 1, 2, ..., n-1 off-diagonal.
%C A374621 a(n) is the number of distinct values of the permanent of an n X n symmetric Toeplitz matrix having 0 on the main diagonal and all the first n-1 primes off-diagonal. (End)
%H A374621 Wikipedia, <a href="http://en.wikipedia.org/wiki/Toeplitz_matrix">Toeplitz Matrix</a>.
%F A374621 a(0) = 1, a(4) = 5, and a(n) = (n-1)! for n > 0 and n <> 4.
%F A374621 a(n) = (n - 1)*a(n-1) for n > 5.
%t A374621 nmax=24; CoefficientList[Series[1-x^4/24-Log[1-x], {x,0,nmax}], x]*Range[0,nmax]!
%Y A374621 Cf. A369833.
%Y A374621 Cf. A374617, A374618, A374619, A374620.
%K A374621 nonn,easy
%O A374621 0,4
%A A374621 _Stefano Spezia_, Jul 14 2024