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 A317095 #49 Sep 11 2018 03:00:05
%S A317095 0,40,80,120,160,200,240,280,320,360,400,440,480,520,560,600,640,680,
%T A317095 720,760,800,840,880,920,960,1000,1040,1080,1120,1160,1200,1240,1280,
%U A317095 1320,1360,1400,1440,1480,1520,1560,1600,1640,1680,1720,1760,1800,1840,1880
%N A317095 a(n) = 40*n.
%C A317095 a(n) is equal to the freshwater zone below sea level for a water table of elevation n above sea level in a simplified freshwater-saltwater interface in a coastal water-table aquifer (cf. Barlow, 2003, p. 14, eq. (2) and p. 15, Fig. B-1 and B-2).
%C A317095 From _Bruno Berselli_, Sep 10 2018: (Start)
%C A317095 After 0, subsequence of A065607: 1/a(n)^2 + 1/(30*n)^2 = 1/(24*n)^2, with n > 0 and a(n) > 30*n.
%C A317095 Also, all positive terms belong to A049094: 2^(40*n)-1 = 1024^(4*n)-1 and (25*41-1)^(4*n)-1 is divisible by 25. (End)
%H A317095 P. M. Barlow, <a href="https://doi.org/10.3133/cir1262">Ground Water in Freshwater-Saltwater Environments of the Atlantic Coast</a>, Circular 1262 (2003).
%H A317095 Wikipedia, <a href="https://en.wikipedia.org/wiki/Aquifer">Aquifer</a>
%H A317095 Wikipedia, <a href="https://en.wikipedia.org/wiki/Saltwater_intrusion">Saltwater intrusion</a>
%H A317095 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F A317095 O.g.f.: 40*x/(1 - x)^2.
%F A317095 E.g.f.: 40*x*exp(x). - _Bruno Berselli_, Sep 10 2018
%F A317095 a(n) = 2*a(n - 1) - a(n - 2) for n > 1. - _Stefano Spezia_, Sep 07 2018
%F A317095 a(n) = A008586(A008592(n)) = 4*A008592(n).
%F A317095 a(n) = A010692(n)*A008586(n) = 10*A008586(n).
%F A317095 a(n) = A008602(A005843(n)) = 20*A005843(n).
%F A317095 a(n) = A007395(n)*A008602(n) = 2*A008602(n).
%t A317095 Table[40 n, {n, 0, 50}] (* or *)
%t A317095 LinearRecurrence[{2, -1}, {0, 40}, 50] (* or *)
%t A317095 CoefficientList[Series[40*x/(1 - x)^2, {x, 0, 50}], x] (* _Stefano Spezia_, Sep 07 2018 *)
%o A317095 (PARI) a(n) = 40*n
%o A317095 (PARI) a(n) = if(n==0, 0, if(n==1, 40, 2*a(n-1)-a(n-2)))
%o A317095 (PARI) concat(0, Vec(40*x/(1-x)^2 + O(x^60)))
%Y A317095 Cf. A005843, A007395, A008586, A008592, A008602, A010692, A049094, A065607.
%Y A317095 Row n = 40 of A004247. Intersection of A008587 and A008590.
%Y A317095 After 0, subsequence of A005101.
%K A317095 nonn,easy
%O A317095 0,2
%A A317095 _Felix Fröhlich_, Sep 07 2018