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 A247016 #22 May 22 2025 10:21:40
%S A247016 0,3,6,28,36,55,66,253,300,325,528,595,630,666,820,903,990,2080,2556,
%T A247016 2628,2850,2926,3003,3655,3828,5050,5253,5356,5565,5886,5995,6328,
%U A247016 6555,6903,8256,8385,20503,22366,23005,23220,23653,25200,26335,26565,28203,28680,28920
%N A247016 Triangular numbers A000217 composed of only curved digits {0, 2, 3, 5, 6, 8, 9}.
%C A247016 Intersection of A000217 and A028374.
%H A247016 K. D. Bajpai, <a href="/A247016/b247016.txt">Table of n, a(n) for n = 1..10000</a>
%e A247016 a(10) = 528 is in the sequence because it is A000217(32) and composed of only curved digits 5, 2 and 8.
%e A247016 a(14) = 820 is in the sequence because it is A000217(40) and composed of only curved digits 8, 2 and 0.
%t A247016 A247016 = {}; Do[t = n*(n + 1)/2; If[Intersection[IntegerDigits[t], {1, 4, 7}] == {}, AppendTo[A247016, t]], {n,0, 500}]; A247016
%t A247016 Select[Accumulate[Range[0,300]],DigitCount[#,10,1]==DigitCount[#,10,4] == DigitCount[ #,10,7] == 0&] (* _Harvey P. Dale_, Apr 18 2019 *)
%o A247016 (Python)
%o A247016 for n in range(2,10**3):
%o A247016 s = str(int(n*(n-1)/2))
%o A247016 if not (s.count('1') + s.count('4') + s.count('7')):
%o A247016 print(int(s),end=', ') # _Derek Orr_, Sep 18 2014
%Y A247016 Cf. A000217, A028374, A034470, A072960.
%K A247016 nonn,base,less
%O A247016 1,2
%A A247016 _K. D. Bajpai_, Sep 09 2014
%E A247016 Added starting number 0 (suggested by D. Orr), added A-number in the name and examples. - _Wolfdieter Lang_, Oct 06 2014