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%I #17 Jul 15 2015 10:18:12
%S 3,22,63,135,555,1301,4607,15441,33852,240488,694409,857993,5563724,
%T 9289707,28048931,129440103,262527982,1982424660,8858170624
%N a(n) is the number of digits in the decimal expansion of Pi needed to contain a repeated n-digit substring.
%H Dave Andersen, <a href="http://www.angio.net/pi/piquery">The Pi-Search Page.</a>
%H 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 We need 3 digits (141) to find the first digit to repeat (the repeated digit is 1).
%e We need 22 digits (1415926535897932384626) to find the first 2 digit repeat (the repeated 2-digit substring is 26).
%Y Cf. A000796 (Pi), A197123 (the repeated substring).
%K base,nonn,hard
%O 1,1
%A _Peter de Rivaz_, Oct 15 2011
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