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 A153220 #15 Aug 23 2025 10:23:44
%S A153220 4,315,360,384,47696,496498,1577526,5607861220,6106488294
%N A153220 Self-locating strings within Pi: numbers n such that the string n is at position n (counting 3 and the decimal point) in decimal digits of Pi.
%C A153220 a(8) > 10^9. - _Vaclav Kotesovec_, Feb 18 2020
%e A153220 a(1)=4 because the 4th character (including the decimal point) in 3.14159... is also a 4.
%t A153220 dpi = RealDigits[Pi, 10, 10000010][[1]]; Select[Range[2, 10000000], FromDigits[Take[dpi, {# - 1, # - 2 + IntegerLength[#]}]] == # &] (* _Vaclav Kotesovec_, Feb 18 2020 *)
%Y A153220 Cf. A057679, A057680, A109513, A109514
%K A153220 base,more,nonn,changed
%O A153220 1,1
%A A153220 _Gil Broussard_, Dec 21 2008
%E A153220 a(7) from _Vaclav Kotesovec_, Feb 18 2020
%E A153220 a(8)-a(9) from _Guixin Lai_, Aug 22 2025