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 A159345 #21 Aug 14 2024 01:49:55 %S A159345 3,22,63,135,555,1301,4607,15441,33852,240488,694409,857993,5563724, %T A159345 9289707,28048931,129440103,262527982,1982424660,8858170624, %U A159345 17601613331 %N A159345 a(n) is the number of digits in the decimal expansion of Pi needed to contain a repeated n-digit substring. %H A159345 Dave Andersen, <a href="http://www.angio.net/pi/piquery">The Pi-Search Page.</a> %H A159345 David H. Bailey, <a href="http://www.davidhbailey.com/dhbpapers/pi.pdf">The computation of to 29,360,000 decimal digits using Borweins' quartically convergent algorithm</a>, Mathematics of Computation, 50(1988), 283-296. %e A159345 We need 3 digits (141) to find the first digit to repeat (the repeated digit is 1). %e A159345 We need 22 digits (1415926535897932384626) to find the first 2 digit repeat (the repeated 2-digit substring is 26). %Y A159345 Cf. A000796 (Pi), A197123 (the repeated substring). %K A159345 base,nonn,hard %O A159345 1,1 %A A159345 _Peter de Rivaz_, Oct 15 2011 %E A159345 a(20) from _Jeff Sponaugle_, Aug 13 2024