The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A232013 Number of iterations of A176341 ("position of n in Pi") until a value is reached for the second time, when starting with n, or -1 if no value is repeated. 6
 4, 1, 12, 4, 13, 14, 11, 10 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS See A232014 for a variant based on A032445 instead of A176341. Some loops: (1), (711939213), (0, 32, 15, 3), (19, 37, 46), (40, 70, 96, 180, 3664, 24717, 15492, 84198, 65489, 3725, 16974, 41702, 3788, 5757, 1958, 14609, 62892, 44745, 9385, 169). See Hans Havermann table (in links) for primary unknown-length evolutions. LINKS Table of n, a(n) for n=0..7. David G. Andersen, Loop Sequences within Pi, on The Pi-Search Page (Search 2*10^8 decimal digits of Pi). Hans Havermann, Information table of n, a(n) for n=0..100. Joaquin Navarro, Les secrets du nombre Pi (Book review, in French). James Taylor, Irrational Numbers Search Engine (Search 2*10^9 decimal digits of Pi). Ady Tzidon, Loops in Pi. EXAMPLE a(0)=4 since A176341(0)=32 (position of the first "0" in Pi's digits), A176341(32)=15 (position of the first "32" in Pi's digits), A176341(15)=3 (position of the first "15" in Pi's digits), A176341(3)=0 (position of the first "3" in Pi's digits); here we find the "0" again after 4 iterations, thus a(0)=4. a(1)=1 since A176341(1)=1 (the first "1" occurs at position 1 in Pi's digits), which already "closes the loop" after 1 iteration. a(2)=12 because the iterations yield 2 > 6 > 7 > 13 > 110 > 174 > 155 > 314 > 0 > 32 > 15 > 3 > 0, here we re-enter the loop (of length 4) after 12 iterations. MATHEMATICA pidigits = First[RealDigits[N[Pi, 10^6]]]; Table[ lst = {}; test = n; steps = 1; While[AppendTo[lst, test]; ! MemberQ[lst, test = First[ First[SequencePosition[pidigits, IntegerDigits[test], 1]]] - 1], steps++ ]; steps, {n, 0, 7}] (* Robert Price, Aug 31 2019 *) PROG (PARI) A232013(n)={my(u=0); for(i=1, 9e9, u+=1<

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 22 14:18 EDT 2024. Contains 371903 sequences. (Running on oeis4.)