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 A134547 #17 Jun 06 2025 00:17:08
%S A134547 29,64,109,164,229,304,389,484,589,704,829,964,1109,1264,1429,1604,
%T A134547 1789,1984,2189,2404,2629,2864,3109,3364,3629,3904,4189,4484,4789,
%U A134547 5104,5429,5764,6109,6464,6829,7204,7589,7984,8389,8804,9229,9664,10109,10564,11029
%N A134547 a(n) = 5*n^2 + 20*n + 4.
%C A134547 Most quintic polynomials x^5 + 5*x*(5*n^2 + 20*n + 4) + 8*(5*n^2 + 20*n + 4) (with the exception of n=0 or -4 when the polynomial is solvable, or n=-2 when it is reducible) have nonsolvable alternating Galois group A_5 (of order 60) over rational numbers.
%H A134547 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A134547 G.f.: -x*(29-23*x+4*x^2)/(-1+x)^3. - _R. J. Mathar_, Nov 14 2007
%F A134547 From _Elmo R. Oliveira_, Jun 04 2025: (Start)
%F A134547 E.g.f.: -4 + (4 + 25*x + 5*x^2)*exp(x).
%F A134547 a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n >= 4. (End)
%p A134547 seq(5*n^2+20*n+4,n=1..40); # _Robert Israel_, May 19 2025
%t A134547 Table[5n^2 + 20n + 4, {n, 1, 30}]
%o A134547 (PARI) a(n)=5*n^2+20*n+4 \\ _Charles R Greathouse IV_, Jun 17 2017
%Y A134547 Cf. A134538.
%K A134547 nonn,easy
%O A134547 1,1
%A A134547 _Artur Jasinski_, Oct 31 2007, Nov 21 2007