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 A047608 #51 Apr 17 2025 16:27:18
%S A047608 4,5,12,13,20,21,28,29,36,37,44,45,52,53,60,61,68,69,76,77,84,85,92,
%T A047608 93,100,101,108,109,116,117,124,125,132,133,140,141,148,149,156,157,
%U A047608 164,165,172,173,180,181,188,189,196,197,204,205,212,213,220,221,228,229
%N A047608 Numbers that are congruent to {4, 5} mod 8.
%H A047608 David Lovler, <a href="/A047608/b047608.txt">Table of n, a(n) for n = 1..10000</a>
%H A047608 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1).
%F A047608 G.f.: x*(4+x+3*x^2) / ( (1+x)*(x-1)^2 ). - _R. J. Mathar_, Sep 22 2016
%F A047608 a(n) = 4n - 3*(1 + (-1)^n)/2 or a(n) = 4n - 3*((n-1) mod 2). - _Heinz Ebert_, Jul 12 2021
%F A047608 Sum_{n>=1} (-1)^(n+1)/a(n) = (sqrt(2)-1)*Pi/16 - log(2)/4 + sqrt(2)*log(sqrt(2)+1)/8. - _Amiram Eldar_, Dec 19 2021
%F A047608 E.g.f.: 3 + ((8*x - 3)*exp(x) - 3*exp(-x))/2. - _David Lovler_, Aug 20 2022
%t A047608 Select[Range[230], MemberQ[{4, 5}, Mod[#, 8]] &] (* _Amiram Eldar_, Dec 19 2021 *)
%o A047608 (PARI) a(n) = 4*n - 3*(1 + (-1)^n)/2 \\ _David Lovler_, Aug 20 2022
%Y A047608 Union of A017113 and A004770.
%K A047608 nonn,easy
%O A047608 1,1
%A A047608 _N. J. A. Sloane_