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A355622
a(n) is the n-digit positive number with no trailing zeros and coprime to its digital reversal R(a(n)) at which abs(a(n)/R(a(n))-Pi) is minimized.
5
1, 92, 581, 5471, 52861, 998713, 7774742, 93630892, 422334431, 9190135292, 45425395441, 472539314051, 5784475521481, 49371008251751, 939253175379892, 9265811239939492, 52949745472445861, 952186420153090303, 9836241210282790313, 36386277546811128511, 442327789252803797041
OFFSET
1,2
COMMENTS
a(n) and R(a(n)) have the same number of digits.
Petr Beckmann wrote that the fraction 92/29, corresponding to the second term of the sequence, appeared as value of Pi in a document written in A.D. 718.
REFERENCES
Petr Beckmann, A History of Pi, 3rd Ed., Boulder, Colorado: The Golem Press (1974): p. 27.
LINKS
EXAMPLE
n fraction approximated value
- ------------------- ------------------
1 1 1
2 92/29 3.1724137931034...
3 581/185 3.1405405405405...
4 5471/1745 3.1352435530086...
5 52861/16825 3.1418127786033...
6 998713/317899 3.1416047235128...
7 7774742/2474777 3.1415929596889...
8 93630892/29803639 3.1415926088757...
9 422334431/134433224 3.1415926690860...
...
MATHEMATICA
nmax=9; a={}; For[n=1, n<=nmax, n++, minim=Infinity; For[k=10^(n-1), k<=10^n-1, k++, If[(dist=Abs[k/FromDigits[Reverse[IntegerDigits[k]]]-Pi]) < minim && Last[IntegerDigits[k]]!=0 && GCD[k, FromDigits[Reverse[IntegerDigits[k]]]]==1, minim=dist; kmin=k]]; AppendTo[a, kmin]]; a
CROSSREFS
Cf. A355623 (denominator or digital reversal).
Sequence in context: A205992 A200425 A107343 * A231300 A176630 A281077
KEYWORD
nonn,base,frac
AUTHOR
Stefano Spezia, Jul 10 2022
EXTENSIONS
a(10)-a(19) from Bert Dobbelaere, Jul 17 2022
a(20)-a(21) from Bert Dobbelaere, Sep 05 2022
STATUS
approved