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 A386858 #19 Aug 15 2025 15:57:57
%S A386858 0,2,5,10,15,22,30,40,50,62,75,90,105,122,140,160,180,202,225,250,275,
%T A386858 302,330,360,390,422,455,490,525,562,600,640,680,722,765,810,855,902,
%U A386858 950,1000,1050,1102,1155,1210,1265,1322,1380,1440,1500,1562,1625,1690,1755
%N A386858 a(n) = floor(5*n^2/8).
%H A386858 Paolo Xausa, <a href="/A386858/b386858.txt">Table of n, a(n) for n = 1..10000</a>
%H A386858 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1,0,1,-2,1).
%F A386858 a(2n) = A032526(n).
%F A386858 a(2n+1) = A028895(n).
%F A386858 a(n) = 2*a(n-1) - a(n-2) + a(n-4) - 2*a(n-5) + a(n-6) for n > 6.
%F A386858 G.f.: -x^2*(2*x^2 + x + 2)/((x - 1)^3*(x + 1)*(x^2 + 1)).
%F A386858 Sum_{n>=2} 1/a(n) = 2/5 + Pi^2/60 + tan(Pi/(2*sqrt(5)))*Pi/(2*sqrt(5)). - _Amiram Eldar_, Aug 15 2025
%t A386858 A386858[n_] := Floor[5*n^2/8]; Array[A386858, 60] (* _Paolo Xausa_, Aug 13 2025 *)
%o A386858 (Python)
%o A386858 def A386858(n): return 5*n**2>>3
%Y A386858 Cf. A032526, A028895.
%K A386858 nonn,easy
%O A386858 1,2
%A A386858 _Chai Wah Wu_, Aug 05 2025