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 A123387 #16 Oct 18 2022 15:22:51
%S A123387 2,3,3,4,5,5,6,6,7,8,8,9,9,9,10,10,11,11,12,12,12,13,13,13,14,14,14,
%T A123387 15,15,15,16,16,17,17,17,17,18,18,18,19,19,19,20,20,20,20,21,21,21,21,
%U A123387 22,22,22,22,23,23,23,23,24,24,24,24,25,25,25,25,26,26,26,26,27,27,27,27
%N A123387 Number of triangular numbers <= n-th prime.
%C A123387 Variant of A057062. - _R. J. Mathar_, Dec 13 2008
%H A123387 G. C. Greubel, <a href="/A123387/b123387.txt">Table of n, a(n) for n = 1..5000</a>
%F A123387 a(n) = A003056(A000040(n)) + 1 = A002024(A000040(n) + 1).
%F A123387 a(n) ~ sqrt(2n log n). - _Charles R Greathouse IV_, Oct 18 2022
%t A123387 f[n_] := Round[Sqrt[2n + 2]]; Table[f[Prime[n]], {n, 90}] (* _Ray Chandler_, Nov 13 2006 *)
%o A123387 (Python)
%o A123387 from math import isqrt
%o A123387 from sympy import prime
%o A123387 def A123387(n): return isqrt(prime(n)+1<<3)+1>>1 # _Chai Wah Wu_, Oct 18 2022
%Y A123387 Cf. A000040, A000217, A002024, A003056.
%K A123387 easy,nonn
%O A123387 1,1
%A A123387 _Giovanni Teofilatto_, Nov 10 2006
%E A123387 Extended by _Ray Chandler_, Nov 13 2006