A159345 - OEIS

A159345

a(n) is the number of digits in the decimal expansion of Pi needed to contain a repeated n-digit substring.

3, 22, 63, 135, 555, 1301, 4607, 15441, 33852, 240488, 694409, 857993, 5563724, 9289707, 28048931, 129440103, 262527982, 1982424660, 8858170624, 17601613331

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..20.

Dave Andersen, The Pi-Search Page.

David H. Bailey, The computation of to 29,360,000 decimal digits using Borweins' quartically convergent algorithm, Mathematics of Computation, 50(1988), 283-296.

EXAMPLE

We need 3 digits (141) to find the first digit to repeat (the repeated digit is 1).

We need 22 digits (1415926535897932384626) to find the first 2 digit repeat (the repeated 2-digit substring is 26).

CROSSREFS

Cf. A000796 (Pi), A197123 (the repeated substring).

Sequence in context: A187694 A104604 A139272 * A006532 A274870 A178492

Adjacent sequences: A159342 A159343 A159344 * A159346 A159347 A159348

KEYWORD

base,nonn,hard

AUTHOR

Peter de Rivaz, Oct 15 2011

EXTENSIONS

a(20) from Jeff Sponaugle, Aug 13 2024

STATUS

approved