cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A089491 Decimal expansion of Buffon's constant 3/Pi.

Original entry on oeis.org

9, 5, 4, 9, 2, 9, 6, 5, 8, 5, 5, 1, 3, 7, 2, 0, 1, 4, 6, 1, 3, 3, 0, 2, 5, 8, 0, 2, 3, 5, 0, 8, 6, 1, 7, 2, 2, 0, 6, 7, 5, 7, 8, 7, 4, 4, 4, 2, 7, 3, 8, 6, 9, 2, 4, 8, 6, 0, 0, 4, 0, 6, 4, 3, 5, 3, 3, 8, 0, 7, 8, 5, 8, 0, 5, 3, 5, 9, 2, 1, 0, 5, 4, 0, 6, 8, 2, 8, 1, 6, 5, 9, 7, 5, 1, 8, 5, 1, 5, 7, 3, 6, 4, 3, 7
Offset: 0

Views

Author

Robert G. Wilson v, Nov 04 2003

Keywords

Comments

Whereas 2/Pi (A060294) is the probability that a needle will land on one of many parallel lines, this is the probability that a needle will land on one of many lines making up a grid.
The probability that the boundary of an equilateral triangle will intersect one of the parallel lines if the triangle edge length l (almost) equals the distance d between each pair of lines. This follows directly from the Weisstein/MathWorld Buffon's Needle Problem link's statement P=p/(Pi*d), where P is the probability of intersection with any convex polygon's boundary if the generalized diameter of that polygon is less than d and p is the perimeter of the polygon. (Take d=l, then p=3d.) - Rick L. Shepherd, Jan 11 2006
Related grid problems are discussed in the Weisstein/MathWorld Buffon-Laplace Needle Problem link. - Rick L. Shepherd, Jan 11 2006
The area of a regular dodecagon circumscribed in a unit-area circle. - Amiram Eldar, Nov 05 2020
From Bernard Schott, Apr 19 2022: (Start)
For any non-obtuse triangle ABC (see Mitrinović and Oppenheim links):
(a/A + b/B + c/C)/(a+b+c) >= 3/Pi,
(a^2/A + b^2/B + c^2/C)/(a^2+b^2+c^2) <= 3/Pi,
where (A,B,C) are the angles (measured in radians) and (a,b,c) the side lengths of this triangle.
Equality stands iff triangle ABC is equilateral. (End)

Examples

			3/Pi = 0.95492965855137201461330258023508617220675787444273869248600...
		

References

  • Joe Portney, Portney's Ponderables, Litton Systems, Inc., Appendix 2, 'Buffon's Needle' by Lawrence R. Weill, 200, pp. 135-138.

Crossrefs

Cf. A000796 (Pi), A060294 (2/Pi).

Programs

  • Mathematica
    RealDigits[ N[ 3/Pi, 111]][[1]]
  • PARI
    3/Pi \\ Michel Marcus, Nov 05 2020

Formula

Equals sinc(Pi/6). - Peter Luschny, Oct 04 2019
From Amiram Eldar, Aug 20 2020: (Start)
Equals Product{k>=1} cos(Pi/(6*2^k)).
Equals Product{k>=1} (1 - 1/(6*k)^2). (End)

A004608 Expansion of Pi in base 9.

Original entry on oeis.org

3, 1, 2, 4, 1, 8, 8, 1, 2, 4, 0, 7, 4, 4, 2, 7, 8, 8, 6, 4, 5, 1, 7, 7, 7, 6, 1, 7, 3, 1, 0, 3, 5, 8, 2, 8, 5, 1, 6, 5, 4, 5, 3, 5, 3, 4, 6, 2, 6, 5, 2, 3, 0, 1, 1, 2, 6, 3, 2, 1, 4, 5, 0, 2, 8, 3, 8, 6, 4, 0, 3, 4, 3, 5, 4, 1, 6, 3, 3, 0, 3, 0, 8, 6, 7, 8, 1, 3, 2, 7, 8, 7, 1, 5, 8, 8, 5, 3, 6, 8, 1, 3, 6, 5, 3
Offset: 1

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Author

Keywords

Examples

			3.12418812407442788645177761731035828516...
		

Crossrefs

Pi in base b: A004601 (b=2), A004602 (b=3), A004603 (b=4), A004604 (b=5), A004605 (b=6), A004606 (b=7), A006941 (b=8), this sequence (b=9), A000796 (b=10), A068436 (b=11), A068437 (b=12), A068438 (b=13), A068439 (b=14), A068440 (b=15), A062964 (b=16), A060707 (b=60).
Cf. A007514.

Programs

  • Mathematica
    RealDigits[Pi, 9, 105][[1]]
    Table[ResourceFunction["NthDigit"][Pi, n, 9], {n, 1, 105}] (* Joan Ludevid, Oct 09 2022 easy to compute a(10000000)=5 with this function; requires Mathematica 12.0+ *)

Extensions

More terms from Robert G. Wilson v, Oct 20 2002

A037001 Positions of the digit '2' in the decimal expansion of Pi (where positions 0, 1, 2,... refer to the digits 3, 1, 4,...).

Original entry on oeis.org

6, 16, 21, 28, 33, 53, 63, 73, 76, 83, 89, 93, 102, 112, 114, 135, 136, 140, 149, 160, 165, 173, 185, 186, 203, 221, 229, 241, 244, 260, 275, 280, 289, 292, 298, 302, 326, 329, 333, 335, 337, 354, 374, 380, 406, 423, 435, 456, 462, 477, 479, 484, 485, 500
Offset: 1

Views

Author

Nicolau C. Saldanha (nicolau(AT)mat.puc-rio.br)

Keywords

Comments

The first few primes in this sequence are 53, 73, 83, 89, 149, 173, 229, 241, 337, 479, 571, 613, 661, 757, 829, 877, 911, 977, 991, ... - M. F. Hasler, Jul 28 2024

Crossrefs

Cf. A000796 (decimal expansion (or digits) of Pi).
Cf. A053746 (= a(n) + 1: the same with different offset).
Cf. A037000, A037002, A037003, A037004, A037005, A036974, A037006, A037007, A037008 (similar for digits 1, ..., 9 and 0).
Cf. A035117 (first occurrence of at least n '1's), A050281 (n '2's), A050282, A050283, A050284, A050286, A050287, A048940 (n '9's).
Cf. A096755 (first occurrence of exactly n '1's), A096756, A096757, A096758, A096759, A096760, A096761, A096762, A096763 (exactly n '9's), A050279 (exactly n '0's).
Cf. A121280 = A068987 - 1: position of "123...n" in Pi's decimals.
Cf. A176341: first occurrence of n in Pi's digits.

Programs

  • Mathematica
    Flatten @ Position[ RealDigits[Pi - 3, 10, 500][[1]], 2] (* Robert G. Wilson v, Mar 07 2011 *)
  • PARI
    A037001_upto(N=999, d=2)={localprec(N+20); [i-1|i<-[1..#N=digits(Pi\10^-N)], N[i]==d]} \\ M. F. Hasler, Jul 28 2024

Formula

a(n) ~ 10*n if Pi is normal, as generally assumed. - M. F. Hasler, Jul 28 2024

A059742 Decimal expansion of e + Pi.

Original entry on oeis.org

5, 8, 5, 9, 8, 7, 4, 4, 8, 2, 0, 4, 8, 8, 3, 8, 4, 7, 3, 8, 2, 2, 9, 3, 0, 8, 5, 4, 6, 3, 2, 1, 6, 5, 3, 8, 1, 9, 5, 4, 4, 1, 6, 4, 9, 3, 0, 7, 5, 0, 6, 5, 3, 9, 5, 9, 4, 1, 9, 1, 2, 2, 2, 0, 0, 3, 1, 8, 9, 3, 0, 3, 6, 6, 3, 9, 7, 5, 6, 5, 9, 3, 1, 9, 9, 4, 1, 7, 0, 0, 3, 8, 6, 7, 2, 8, 3, 4, 9, 5, 4, 0, 9, 6, 1
Offset: 1

Views

Author

Fabian Rothelius, Feb 10 2001

Keywords

Comments

It is not presently known if this number is rational or irrational.

Examples

			5.859874482048838473822930854632165381954416493075065395941912220031893...
		

Crossrefs

Cf. A001113, A000796, A058651 (continued fraction).

Programs

  • Maple
    Digits := 200: with(numtheory): it := evalf((Pi+exp(1))/10, 200): for i from 1 to 20 0 do printf(`%d,`,floor(10*it)): it := 10*it-floor(10*it): od:
  • Mathematica
    RealDigits[E + Pi, 10, 105][[1]] (* Robert G. Wilson v, Sep 24 2004 *)
  • PARI
    { default(realprecision, 20080); x=Pi+exp(1); for (n=1, 20000, d=floor(x); x=(x-d)*10; write("b059742.txt", n, " ", d)); } \\ Harry J. Smith, May 31 2009

Extensions

More terms from James Sellers, Feb 13 2001

A090771 Numbers that are congruent to {1, 9} mod 10.

Original entry on oeis.org

1, 9, 11, 19, 21, 29, 31, 39, 41, 49, 51, 59, 61, 69, 71, 79, 81, 89, 91, 99, 101, 109, 111, 119, 121, 129, 131, 139, 141, 149, 151, 159, 161, 169, 171, 179, 181, 189, 191, 199, 201, 209, 211, 219, 221, 229, 231, 239, 241, 249, 251, 259, 261, 269, 271, 279, 281
Offset: 1

Views

Author

Giovanni Teofilatto, Feb 07 2004

Keywords

Comments

Cf. property described by Gary Detlefs in A113801: more generally, these numbers are of the form (2*h*n + (h-4)*(-1)^n - h)/4 (h, n natural numbers), therefore ((2*h*n + (h-4)*(-1)^n - h)/4)^2-1 == 0 (mod h); in this case, a(n)^2 - 1 == 0 (mod 10). - Bruno Berselli, Nov 17 2010

Crossrefs

Cf. A056020 (n = 1 or 8 mod 9), A175885 (n = 1 or 10 mod 11).
Cf. A045468 (primes), A195142 (partial sums).

Programs

Formula

a(n) = sqrt(40*A057569(n) + 1). - Gary Detlefs, Feb 22 2010
From Bruno Berselli, Sep 16 2010 - Nov 17 2010: (Start)
G.f.: x*(1 + 8*x + x^2)/((1 + x)*(1 - x)^2).
a(n) = (10*n + 3*(-1)^n - 5)/2.
a(n) = -a(-n + 1) = a(n-1) + a(n-2) - a(n-3) = a(n-2) + 10.
a(n) = 10*A000217(n-1) + 1 - 2*Sum_{i=1..n-1} a(i) for n > 1. (End)
a(n) = 10*n - a(n-1) - 10 (with a(1) = 1). - Vincenzo Librandi, Nov 16 2010
a(n) = sqrt(10*A132356(n-1) + 1). - Ivan N. Ianakiev, Nov 09 2012
Sum_{n>=1} (-1)^(n+1)/a(n) = (Pi/10)*cot(Pi/10) = A000796 * A019970 / 10 = sqrt(5 + 2*sqrt(5))*Pi/10. - Amiram Eldar, Dec 04 2021
E.g.f.: 1 + ((10*x - 5)*exp(x) + 3*exp(-x))/2. - David Lovler, Sep 03 2022
From Amiram Eldar, Nov 23 2024: (Start)
Product_{n>=1} (1 - (-1)^n/a(n)) = sqrt(phi+2) (A188593).
Product_{n>=2} (1 + (-1)^n/a(n)) = Pi*phi/5 = A094888/10. (End)

Extensions

Edited and extended by Ray Chandler, Feb 10 2004

A004603 Expansion of Pi in base 4.

Original entry on oeis.org

3, 0, 2, 1, 0, 0, 3, 3, 3, 1, 2, 2, 2, 2, 0, 2, 0, 2, 0, 1, 1, 2, 2, 0, 3, 0, 0, 2, 0, 3, 1, 0, 3, 0, 1, 0, 3, 0, 1, 2, 1, 2, 0, 2, 2, 0, 2, 3, 2, 0, 0, 0, 3, 1, 3, 0, 0, 1, 3, 0, 3, 1, 0, 1, 0, 2, 2, 1, 0, 0, 0, 2, 1, 0, 3, 2, 0, 0, 2, 0, 2, 0, 2, 2, 1, 2, 1, 3, 3, 0, 3, 0, 1, 3, 1, 0, 0, 0, 0, 2, 0, 0, 2, 3, 2
Offset: 1

Views

Author

Keywords

Comments

Theoretically, this sequence could be used to encode a given number of digits of Pi as a DNA sequence, which could then be read back from one helix. The value read back from the other helix would of course depend on the assignment of G, A, C, T to the digits 0, 1, 2, 3. - Alonso del Arte, Nov 07 2011

Examples

			3.02100333122220202011220300203103010301...
		

Crossrefs

Pi in base b: A004601 (b=2), A004602 (b=3), this sequence (b=4), A004604 (b=5), A004605 (b=6), A004606 (b=7), A006941 (b=8), A004608 (b=9), A000796 (b=10), A068436 (b=11), A068437 (b=12), A068438 (b=13), A068439 (b=14), A068440 (b=15), A062964 (b=16), A060707 (b=60).
Cf. A007514.
Cf. A004595, A004541. - Jason Kimberley, Dec 01 2012

Programs

  • Mathematica
    RealDigits[Pi, 4, 100][[1]]
    Table[ResourceFunction["NthDigit"][Pi, n, 4], {n, 1, 100}] (* Joan Ludevid, Jul 04 2022; easy to compute a(10000000)=2 with this function; requires Mathematica 12.0+ *)

Formula

a(n) = 2*A004601(2n) + A004601(2n+1). - Jason Kimberley, Nov 08 2012

A037007 Positions of the digit '9' in the decimal expansion of Pi, where positions 0, 1, 2,... correspond to digits 3, 1, 4, ....

Original entry on oeis.org

5, 12, 14, 30, 38, 42, 44, 45, 55, 58, 62, 79, 80, 100, 122, 129, 144, 169, 180, 187, 190, 193, 199, 208, 214, 247, 249, 259, 284, 294, 328, 331, 336, 341, 353, 356, 388, 391, 399, 414, 416, 418, 422, 433, 440, 459, 460, 465, 482, 487, 496, 498, 501, 527
Offset: 1

Views

Author

Nicolau C. Saldanha (nicolau(AT)mat.puc-rio.br)

Keywords

Comments

Primes in this sequence are 5, 79, 193, 199, 331, 353, 433, 487, 941, ... - M. F. Hasler, Jul 29 2024

Examples

			The first digit '9' occurs in 3.1415926... at the 5th place after the decimal point, whence a(1) = 5.
		

Crossrefs

Cf. A000796 (decimals of Pi).
Cf. A053753 (variant with all values increased by 1).
Cf. A037000, A037001, A037002, A037003, A037004, A037005, A036974, A037006, A037008 (similar for digits 1, ..., 8 and 0).
Cf. A048940, A096763 (starting position of at least/exactly n '9's).

Programs

  • Mathematica
    Flatten @ Position[ RealDigits[Pi - 3, 10, 500][[1]], 9] (* Robert G. Wilson v, Mar 07 2011 *)
  • PARI
    A037007_upto(N=999, d=9)={localprec(N+20); [i-1|i<-[1..#N=digits(Pi\10^-N)], N[i]==d]} \\ M. F. Hasler, Jul 29 2024

Formula

a(n) = A053753(n) - 1. - M. F. Hasler, Mar 20 2017
a(n) ~ 10*n if Pi is normal (as generally assumed, but yet unproved). - M. F. Hasler, Jul 29 2024

A060707 Base-60 (Babylonian or sexagesimal) expansion of Pi.

Original entry on oeis.org

3, 8, 29, 44, 0, 47, 25, 53, 7, 24, 57, 36, 17, 43, 4, 29, 7, 10, 3, 41, 17, 52, 36, 12, 14, 36, 44, 51, 50, 15, 33, 7, 23, 59, 9, 13, 48, 22, 12, 21, 45, 22, 56, 47, 39, 44, 28, 37, 58, 23, 21, 11, 56, 33, 22, 40, 42, 31, 6, 6, 3, 46, 16, 52, 2, 48, 33, 24, 38, 33, 22, 1, 0, 1
Offset: 1

Views

Author

Robert G. Wilson v, Feb 05 2001

Keywords

References

  • Mohammad K. Azarian, Al-Risala al-Muhitiyya: A Summary, Missouri Journal of Mathematical Sciences, Vol. 22, No. 2, 2010, pp. 64-85.
  • Mohammad K. Azarian, The Introduction of Al-Risala al-Muhitiyya: An English Translation, International Journal of Pure and Applied Mathematics, Vol. 57, No. 6, 2009, pp. 903-914.
  • Mohammad K. Azarian, Al-Kashi's Fundamental Theorem, International Journal of Pure and Applied Mathematics, Vol. 14, No. 4, 2004, pp. 499-509. Mathematical Reviews, MR2005b:01021 (01A30), February 2005, p. 919. Zentralblatt MATH, Zbl 1059.01005.
  • Mohammad K. Azarian, Meftah al-hesab: A Summary, MJMS, Vol. 12, No. 2, Spring 2000, pp. 75-95. Mathematical Reviews, MR 1 764 526. Zentralblatt MATH, Zbl 1036.01002.
  • Mohammad K. Azarian, A Summary of Mathematical Works of Ghiyath ud-din Jamshid Kashani, Journal of Recreational Mathematics, Vol. 29(1), pp. 32-42, 1998.

Crossrefs

Pi in base b: A004601 (b=2), A004602 (b=3), A004603 (b=4), this sequence (b=5), A004605 (b=6), A004606 (b=7), A006941 (b=8), A004608 (b=9), A000796 (b=10), A068436 (b=11), A068437 (b=12), A068438 (b=13), A068439 (b=14), A068440 (b=15), A062964 (b=16), A060707 (b=60). - Jason Kimberley, Dec 06 2012

Programs

  • Mathematica
    RealDigits[ Pi, 60, 75][[1]]
  • PARI
    { default(realprecision, 17900); x=Pi; for (n=1, 10000, d=floor(x); x=(x-d)*60; write("b060707.txt", n, " ", d)); } \\ Harry J. Smith, Jul 09 2009

A068440 Expansion of Pi in base 15.

Original entry on oeis.org

3, 2, 1, 12, 13, 1, 13, 12, 4, 6, 12, 2, 11, 7, 14, 5, 0, 8, 4, 8, 4, 7, 7, 3, 14, 0, 6, 9, 1, 9, 13, 1, 14, 5, 0, 9, 6, 3, 13, 11, 7, 9, 12, 6, 9, 7, 3, 9, 14, 10, 3, 7, 3, 1, 14, 7, 9, 12, 13, 14, 1, 0, 10, 8, 14, 13, 4, 12, 6, 3, 0, 10, 8, 3, 11, 9, 11, 5, 13, 10, 4, 6, 4, 10, 9, 1, 5, 2
Offset: 1

Views

Author

Benoit Cloitre, Mar 09 2002

Keywords

Examples

			3.21cd1dc46c2b...
		

Crossrefs

Pi in base b: A004601 (b=2), A004602 (b=3), A004603 (b=4), A004604 (b=5), A004605 (b=6), A004606 (b=7), A006941 (b=8), A004608 (b=9), A000796 (b=10), A068436 (b=11), A068437 (b=12), A068438 (b=13), A068439 (b=14), this sequence (b=15), A062964 (b=16), A060707 (b=60).
Cf. A007514.

Programs

  • Mathematica
    RealDigits[ N[ Pi, 115], 15] [[1]]
    RealDigits[Pi,15,120][[1]] (* Harvey P. Dale, Aug 05 2025 *)

A073233 Decimal expansion of Pi^Pi.

Original entry on oeis.org

3, 6, 4, 6, 2, 1, 5, 9, 6, 0, 7, 2, 0, 7, 9, 1, 1, 7, 7, 0, 9, 9, 0, 8, 2, 6, 0, 2, 2, 6, 9, 2, 1, 2, 3, 6, 6, 6, 3, 6, 5, 5, 0, 8, 4, 0, 2, 2, 2, 8, 8, 1, 8, 7, 3, 8, 7, 0, 9, 3, 3, 5, 9, 2, 2, 9, 3, 4, 0, 7, 4, 3, 6, 8, 8, 8, 1, 6, 9, 9, 9, 0, 4, 6, 2, 0, 0, 7, 9, 8, 7, 5, 7, 0, 6, 7, 7, 4, 8, 5, 4, 3, 6, 8, 1
Offset: 2

Views

Author

Rick L. Shepherd, Jul 21 2002

Keywords

Comments

A weak form of Schanuel's Conjecture implies that Pi^Pi is transcendental--see Marques and Sondow (2012).

Examples

			36.4621596072079117709908260226...
		

Crossrefs

Cf. A000796 (Pi), A073234 (Pi^Pi^Pi), A073237 (ceil(Pi^Pi^...^Pi), n Pi's), A073238 (Pi^(1/Pi)), A073239 ((1/Pi)^Pi), A073240 ((1/Pi)^(1/Pi)), A073243 (limit of (1/Pi)^(1/Pi)^...^(1/Pi)), A073236 (Pi analog of A004002).
Cf. A073226 (e^e).
Cf. A049006 (i^i), A116186 (real part of i^i^i).
Cf. A194555 (real part of i^e^Pi).

Programs

  • Mathematica
    RealDigits[N[Pi^Pi,200]] (* Vladimir Joseph Stephan Orlovsky, May 27 2010 *)
  • PARI
    Pi^Pi
    
  • PARI
    { default(realprecision, 20080); x=Pi^Pi/10; for (n=2, 20000, d=floor(x); x=(x-d)*10; write("b073233.txt", n, " ", d)); } \\ Harry J. Smith, Apr 30 2009
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