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 A371381 #21 Mar 21 2024 12:33:15 %S A371381 2,8,13,25,41,52,74,89,117,149,170,208,250,277,325,356,410,468,505, %T A371381 569,610,680,754,801,881,965,1018,1108,1165,1261,1361,1424,1530,1640, %U A371381 1709,1825,1898,2020,2146,2225,2357,2440,2578,2720,2809,2957,3109,3204,3362,3461 %N A371381 Main diagonal of A219875. %H A371381 Paolo Xausa, <a href="/A371381/b371381.txt">Table of n, a(n) for n = 1..10000</a> %F A371381 a(n) = n^2 + ceiling(n/(1 + sqrt(5))/2)^2 = n^2 + A019446(n)^2. %t A371381 Array[#^2 + Ceiling[# / GoldenRatio]^2 &, 100] %o A371381 (Python) %o A371381 from math import isqrt %o A371381 def A371381(n): return (n<<1)*(n-1)+1+(q:=n+isqrt(5*n**2)>>1)*(q-(n-1<<1)) # _Chai Wah Wu_, Mar 21 2024 %Y A371381 Cf. A219875. %Y A371381 Cf. A001622, A019446, A101332, A101863, A101867, A371382. %K A371381 nonn,easy %O A371381 1,1 %A A371381 _Paolo Xausa_, Mar 20 2024