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 A374426 #15 Jul 31 2024 09:09:03
%S A374426 1,4,8,12,18,24,32,40,49,59,71,83,97,111,126,142,160,178,198,218,239,
%T A374426 261,285,309,334,360,387,415,445,475,507,539,572,606,641,677,715,753,
%U A374426 792,832,874,916,960,1004,1049,1095,1143,1191,1240,1290,1341,1393,1447
%N A374426 a(n) = n*(n + 1)/2 + pi(n), where pi(n) = A000720(n) is the prime counting function.
%H A374426 James C. McMahon, <a href="/A374426/b374426.txt">Table of n, a(n) for n = 1..10000</a>
%F A374426 a(n) = A000217(n) + A000720(n).
%F A374426 a(1) = 1; for n > 1: a(n) = a(n-1) + n + A010051(n).
%t A374426 Table[n(n+1)/2+PrimePi[n],{n,53}]
%o A374426 (PARI) a(n) = n*(n+1)/2 + primepi(n); \\ _Michel Marcus_, Jul 31 2024
%Y A374426 Cf. A000217, A000720, A010051, A256885.
%Y A374426 Partial sums of A014683.
%K A374426 nonn
%O A374426 1,2
%A A374426 _James C. McMahon_, Jul 08 2024