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 A139595 #13 Apr 20 2024 10:27:29
%S A139595 0,5,13,26,42,63,87,116,148,185,225,270,318,371,427,488,552,621,693,
%T A139595 770,850,935,1023,1116,1212,1313,1417,1526,1638,1755,1875,2000,2128,
%U A139595 2261,2397,2538,2682,2831,2983,3140,3300,3465,3633,3806
%N A139595 A139277(n) followed by A139273(n+1).
%C A139595 Sequence found by reading the line from 0, in the direction 0, 5,... and the same line from 0, in the direction 0, 13,..., in the square spiral whose vertices are the triangular numbers A000217.
%H A139595 Omar E. Pol, <a href="http://www.polprimos.com">Determinacion geometrica de los numeros primos y perfectos</a>.
%H A139595 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,-2,1)
%F A139595 Array read by rows: row n gives 8*n^2 + 5n, 8*(n+1)^2 - 3(n+1).
%F A139595 G.f.: -x*(5+3*x) / ( (1+x)*(x-1)^3 ). - _R. J. Mathar_, Feb 13 2011
%e A139595 Array begins:
%e A139595 0, 5
%e A139595 13, 26
%e A139595 42, 63
%e A139595 87, 116
%t A139595 LinearRecurrence[{2,0,-2,1},{0,5,13,26},50] (* _Harvey P. Dale_, Jul 31 2021 *)
%Y A139595 Cf. A000217, A046092, A139273, A139277, A077221, A139591, A139592, A139593, A139596, A139597, A139598.
%K A139595 easy,nonn
%O A139595 0,2
%A A139595 _Omar E. Pol_, May 03 2008