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 A153228 #10 Jan 30 2022 15:58:42
%S A153228 1,2,3,85,200,447263
%N A153228 Numbers k such that the string k is found at position 3k in the decimal digits of Pi.
%e A153228 a(4) = 85 because 85 occurs at offset 255 (3*85) after the decimal in the digits of Pi.
%o A153228 (Python)
%o A153228 from sympy import S
%o A153228 # download https://stuff.mit.edu/afs/sipb/contrib/pi/pi-billion.txt, then
%o A153228 #with open('pi-billion.txt', 'r') as f: pi_digits = f.readline()
%o A153228 pi_digits = str(S.Pi.n(3*10**5+2))[:-2] # alternative to above
%o A153228 pi_digits = pi_digits.replace(".", "")
%o A153228 def afind():
%o A153228 for k in range(1, len(pi_digits)):
%o A153228 sk = str(k)
%o A153228 if sk == pi_digits[3*k:3*k+len(sk)]:
%o A153228 print(k, end=", ")
%o A153228 afind() # _Michael S. Branicky_, Jan 30 2022
%Y A153228 Cf. A057679, A057680, A109513, A109514, A153227.
%K A153228 base,more,nonn
%O A153228 1,2
%A A153228 _Gil Broussard_, Dec 21 2008
%E A153228 a(6) corrected by _Michael S. Branicky_, Jan 30 2022