A245331 Number of truncated Pi decimal digits that yield record approximations to Pi when the concatenation of the first half of the digits is divided by the second half.

2, 23, 87, 157, 1523, 3445551, 26620870, 30512347, 72713283, 344661698, 1129330411, 3886591581, 5085084202, 11916345303, 15510679381

Offset

1,1

Comments

For odd terms, the number of digits in the first "half" is one more than in the second half. Even terms imply the second half begins with 1; odd terms, with 9.

The second-half numbers:

1 1

2 97932384626

3 99375105820974944592..

4 99862803482534211706..

5 99999983729780499510..

6 99999993176688420006..

7 10000000420467135547..

8 99999998414267344764..

9 99999999542282360035..

10 10000000012202360559..

11 99999999941927584272..

12 99999999948261395946..

13 10000000002413899137..

14 99999999975954453917..

15 99999999988383727123..

Links

Table of n, a(n) for n=1..15.

Example

a(1) is 2 because 3/1 (1+1 digits) provides the first approximation to Pi. a(2) is 23 because 314159265358/97932384626 (12+11 digits) provides the next better approximation.

Crossrefs

Cf. A000796, A048940, A193940.

Sequence in context: A099134 A069152 A131464 * A270868 A239186 A238185

Adjacent sequences: A245328 A245329 A245330 * A245332 A245333 A245334

Keyword

nonn,base

Author

Eric Angelini and Hans Havermann, Jul 18 2014

Extensions

a(12)-a(15) from Hans Havermann, Jul 19 2014

Status

approved