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.

Showing 1-10 of 28 results. Next

A257574 Continued square root map applied to the sequence of positive even numbers, (2, 4, 6, 8, ...).

Original entry on oeis.org

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

Views

Author

N. J. A. Sloane, May 02 2015

Keywords

Comments

The continued square root or CSR map applied to a sequence b = (b(1), b(2), b(3), ...) is the number CSR(b) := sqrt(b(1)+sqrt(b(2)+sqrt(b(3)+sqrt(b(4)+...)))).
Taking out a factor sqrt(2), one gets CSR(2, 4, 6, 8, ...) = sqrt(2) CSR(1, 1, 3/8, 1/32, ...) < A002193*A001622 = (sqrt(5)+1)/sqrt(2). - M. F. Hasler, May 01 2018

Examples

			sqrt(2 + sqrt(4 + sqrt(6 + sqrt(8 + ...)))) = 2.1584768723110397656558534...
		

Crossrefs

Programs

  • PARI
    (CSR(v,s)=forstep(i=#v,1,-1,s=sqrt(v[i]+s));s); t=0;for(N=5,oo,(t==t=Str(CSR([1..2*N]*2)))&&break;print(2*N": "t)) \\ Allows to see the convergence, which is reached when length of vector ~ precision [given as number of digits]. Using Str() to avoid infinite loop when internal representation is "fluctuating". - M. F. Hasler, May 04 2018

Extensions

a(27)-a(87) from Hiroaki Yamanouchi, May 03 2015
Edited by M. F. Hasler, May 01 2018

A105546 Decimal expansion of prime nested radical.

Original entry on oeis.org

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

Views

Author

Jonathan Vos Post, Apr 12 2005

Keywords

Comments

sqrt(1 + sqrt(2 + sqrt(3 + sqrt(4 + ...)))) = 1.75793275661800...
"It was discovered by T. Vijayaraghavan that the infinite radical, sqrt( a_1 + sqrt( a_2 + sqrt ( a_3 + sqrt( a_4 + ... )))) where a_n >= 0, will converge to a limit if and only if the limit of log(a_n)/2^n exists." [Clawson, 229; cf. A072449].
We know the asymptotic limit of primes and hence that the Prime Nested Radical converges.
Clawson misstates Vijayaraghavan's theorem. Vijayaraghavan proved that for a_n > 0, the infinite radical sqrt(a_1 + sqrt(a_2 + sqrt(a_3 + ...))) converges if and only if limsup (log a_n)/2^n < infinity. (For example, suppose a_n = 1 if n is odd, and a_n = e^2^n if n is even. Then (log a_n)/2^n = 0, 1, 0, 1, 0, 1, ... for n >= 1, so the limit does not exist. However, limsup (log a_n)/2^n = 1 and the infinite radical converges.) - Jonathan Sondow, Mar 25 2014

Examples

			2.10359749633989726261993964968532544404216228824001387298687284563...
		

References

  • Calvin C. Clawson, "Mathematical Mysteries, the beauty and magic of numbers," Perseus Books, Cambridge, Mass., 1996, pages 142 and 229.
  • S. R. Finch, Analysis of a Radical Expansion, Section 1.2.1 in Mathematical Constants. Cambridge, England: Cambridge University Press, p. 8, 2003.

Crossrefs

A105548 is the continued fraction representation of this prime nested radical.
A105815 is the similar semiprime nested radical.
A105817 is the Fibonacci nested radical.

Programs

  • Mathematica
    RealDigits[Fold[Sqrt[#1 + #2] &, 0, Reverse[Prime[Range[ 80]]]], 10, 111][[1]] (* Robert G. Wilson v, May 31 2005 *)

Formula

sqrt(2 + sqrt(3 + sqrt(5 + sqrt(7 + sqrt(11 + ... + sqrt(prime(n) + ...)))).

Extensions

Crossrefs corrected by Jaroslav Krizek, Jan 03 2015

A099874 Decimal expansion of a nested radical: CubeRoot(1 + CubeRoot(2 + CubeRoot(3 + CubeRoot(4 + ...

Original entry on oeis.org

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

Views

Author

Mark Hudson (mrmarkhudson(AT)hotmail.com), Nov 02 2004

Keywords

Examples

			1.365300948604002967552742168986737...
		

Crossrefs

Cf. A072449 for version using square root rather than cube root.

Programs

  • Mathematica
    RealDigits[ Fold[(#1 + #2)^(1/3) &, 0, Reverse[Range[100]]], 10, 111][[1]]
  • PARI
    t=0; forstep(n=200,1,-1,t=(t+n)^(1/3)); t

A099876 Decimal expansion of a nested radical: sqrt(1! + sqrt(2! + sqrt(3! + ...

Original entry on oeis.org

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

Views

Author

Mark Hudson (mrmarkhudson(AT)hotmail.com), Nov 02 2004

Keywords

Examples

			1.82701471760859222637384319285...
		

Crossrefs

Programs

  • Mathematica
    RealDigits[Fold[Sqrt[#1 + #2] &, 0, Reverse[Range[100]!]], 10, 111][[1]]
  • PARI
    t=0; forstep(n=300,1,-1,t=sqrt(t+n!)); t \\ gives more than enough correct digits for the number given here.

A099879 Decimal expansion of a nested radical: sqrt(1^2 + sqrt(2^2 + sqrt(3^2 + ...

Original entry on oeis.org

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

Views

Author

Mark Hudson (mrmarkhudson(AT)hotmail.com), Nov 03 2004

Keywords

Examples

			1.94265542276398732822141329141266723768807363...
		

Crossrefs

Cf. A072449, A099874, A099876 to A099878 for other nested radicals.

Programs

  • Mathematica
    k = 64; r = 65; While[k > 0, r = Sqrt[k^2 + r]; k-- ]; RealDigits[r, 10, 111][[1]] (* Robert G. Wilson v, Nov 04 2004 *)
  • PARI
    t=0; forstep(n=100,1,-1,t=sqrt(t+n^2)); print(t)
    
  • PARI
    \\ We need about b/log(b) steps, where epsilon = 2^-b.
    my(b=bitprecision(1.),t); forstep(n=b\log(b)+9,1,-1, t=sqrt(t+n^2)); t \\ Charles R Greathouse IV, Aug 19 2025

A105817 Decimal expansion of the Fibonacci nested radical.

Original entry on oeis.org

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

Views

Author

Jonathan Vos Post, Apr 21 2005

Keywords

Comments

The continued fraction expression of this is A105818. "It was discovered by T. Vijayaraghavan that the infinite radical, sqrt( a_1 + sqrt( a_2 + sqrt ( a_3 + sqrt( a_4 + ... where a_n => 0, will converge to a limit if and only if the limit of (ln a_n)/2^n exists." [Clawson, 229; Sloane]. We know the asymptotic limit of Fibonacci numbers is Phi^n (Binet expansion) and that Phi^n < 2^n and hence that the Fibonacci Nested Radical converges.
Clawson misstates Vijayaraghavan's theorem. Vijayaraghavan proved that for a_n > 0, the infinite radical sqrt(a_1 + sqrt(a_2 + sqrt(a_3 + ...))) converges if and only if limsup (log a_n)/2^n < infinity. (For example, suppose a_n = 1 if n is odd, and a_n = e^2^n if n is even. Then (log a_n)/2^n = 0, 1, 0, 1, 0, 1, ... for n >= 1, so the limit does not exist. However, limsup (log a_n)/2^n = 1 and the infinite radical converges.) - Jonathan Sondow, Mar 25 2014

Examples

			1.66198246232781155796760608181513129505616756246503500829906806743...
		

References

  • Calvin C. Clawson, "Mathematical Mysteries, the beauty and magic of numbers," Perseus Books, Cambridge, Mass., 1996, pages 142 & 229.
  • S. R. Finch, "Analysis of a Radical Expansion." Section 1.2.1 in Mathematical Constants. Cambridge, England: Cambridge University Press, p. 8, 2003.

Crossrefs

Programs

  • Mathematica
    RealDigits[ Fold[ Sqrt[ #1 + #2] &, 0, Reverse[ Fibonacci[ Range[50]]]], 10, 111][[1]] (* Robert G. Wilson v, Apr 21 2005 *)

Formula

Sqrt(1 + sqrt(1 + sqrt(2 + sqrt(3 + sqrt(5 + ... + sqrt(Fibonacci(n)=A000045)))).

A099877 Decimal expansion of nested radical: Sqrt(1^2 + CubeRoot(2^3 + 4thRoot(3^4 + 5thRoot(4^5 + ...

Original entry on oeis.org

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

Views

Author

Mark Hudson (mrmarkhudson(AT)hotmail.com), Nov 02 2004

Keywords

Examples

			1.7962268369357180316400150423265975895...
		

Crossrefs

Programs

  • PARI
    t=0:forstep(n=100,1,-1,t=(t+n^(n+1))^(1/(n+1)))

A105815 Decimal expansion of the semiprime nested radical.

Original entry on oeis.org

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

Views

Author

Jonathan Vos Post, Apr 21 2005

Keywords

Comments

The semiprime nested radical is defined by the infinite recursion: sqrt(4 + sqrt(6 + sqrt(9 + sqrt(10 + sqrt(14 + ... + sqrt(semiprime(n))))). This converges by the criterion of T. Vijayaraghavan that "the infinite radical, sqrt( a_1 + sqrt( a_2 + sqrt ( a_3 + sqrt( a_4 + ... where a_n => 0, will converge to a limit if and only if the limit of (ln a_n)/2^n exists." [Clawson, 229; Sloane A072449]. The continued fraction representation of this constant is A105816.
Clawson misstates Vijayaraghavan's theorem. Vijayaraghavan proved that for a_n > 0, the infinite radical sqrt(a_1 + sqrt(a_2 + sqrt(a_3 + ...))) converges if and only if limsup (log a_n)/2^n < infinity. (For example, suppose a_n = 1 if n is odd, and a_n = e^2^n if n is even. Then (log a_n)/2^n = 0, 1, 0, 1, 0, 1, ... for n >= 1, so the limit does not exist. However, limsup (log a_n)/2^n = 1 and the infinite radical converges.) - Jonathan Sondow, Mar 25 2014

Examples

			2.66352563480685654498944673272195514599922982689272932914833705868...
		

References

  • Calvin C. Clawson, "Mathematical Mysteries, the beauty and magic of numbers," Perseus Books, Cambridge, Mass., 1996, pages 142 & 229.
  • Steven R. Finch, Analysis of a Radical Expansion, Section 1.2.1 in Mathematical Constants. Cambridge, England: Cambridge University Press, 2003, p. 8.

Crossrefs

For other nested radicals, see A072449, A083869, A099874, A099876, A099877, A099878, A099879, A105546, A105548, A105816, A239349.
Cf. A001358.

Programs

  • Mathematica
    fQ[n_] := Plus @@ Flatten[ Table[ #[[2]], {1}] & /@ FactorInteger[n]] == 2; RealDigits[ Fold[ Sqrt[ #1 + #2] &, 0, Reverse[ Select[ Range[260], fQ[ # ] &]]], 10, 111][[1]] (* Robert G. Wilson v, May 31 2005 *)

Formula

Limit_{n -> infinity} sqrt(4 + sqrt(6 + sqrt(9 + sqrt(10 + sqrt(14 + ... + sqrt(semiprime(n))))), where semiprime(n) = A001358(n).

A099878 Decimal expansion of a nested radical: Sqrt(1 + CubeRoot(2 + 4thRoot(3 + 5thRoot(4 + ...

Original entry on oeis.org

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

Views

Author

Mark Hudson (mrmarkhudson(AT)hotmail.com), Nov 03 2004

Keywords

Examples

			1.58454170990556500250912545055...
		

Crossrefs

Cf. A072449, A099874, A099876, A099877 for other nested radicals.

Programs

  • Mathematica
    k = 43; r = 44; While[k > 0, r = (k + r)^(1/(k + 1)); k-- ]; RealDigits[r, 10, 111][[1]] (* Robert G. Wilson v, Nov 04 2004 *)
  • PARI
    t=0;forstep(n=100,1,-1,t=(t+n)^(1/(n+1)));print(t)

A105548 Continued fraction expansion of prime nested radical A105546.

Original entry on oeis.org

2, 9, 1, 1, 1, 7, 3, 5, 4, 1, 1, 1, 3, 2, 2, 1, 1, 1, 1, 15, 1, 3, 1, 41, 6, 1, 3, 1, 3, 10, 1, 1, 1, 9, 9, 1, 25, 1, 3, 1, 1, 2, 2, 2, 1, 34, 59, 2, 2, 2, 1, 2, 2, 3, 3, 1, 5, 2, 21, 3, 4, 10, 1, 3, 20, 2, 3, 2, 1, 4, 7, 1, 6, 1, 6, 3, 4, 1, 3, 5, 6, 1, 1, 4, 1, 3, 6, 25, 7, 2, 1, 1, 2, 1, 6, 1, 1, 7, 1, 3, 2
Offset: 0

Views

Author

Jonathan Vos Post, Apr 14 2005

Keywords

Comments

Records are: 9,15,41,59,117,153,599,1663,8212,..., . Robert G. Wilson v: "It would appear superficially that this constant is normal." Sqrt(1 + sqrt(2 + sqrt(3 + sqrt(4 + ... = ~ 1.75793275661800... "It was discovered by T. Vijayaraghavan that the infinite radical, sqrt( a_1 + sqrt( a_2 + sqrt ( a_3 + sqrt( a_4 + ... where a_n => 0, will converge to a limit if and only if the limit of (ln a_n)/2^n exists." [Clawson, 229; A072449] We know the asymptotic limit of primes and hence that the Prime Nested Radical converges.
Clawson misstates Vijayaraghavan's theorem. Vijayaraghavan proved that for a_n > 0, the infinite radical sqrt(a_1 + sqrt(a_2 + sqrt(a_3 + ...))) converges if and only if limsup (log a_n)/2^n < infinity. (For example, suppose a_n = 1 if n is odd, and a_n = e^2^n if n is even. Then (log a_n)/2^n = 0, 1, 0, 1, 0, 1, ... for n >= 1, so the limit does not exist. However, limsup (log a_n)/2^n = 1 and the infinite radical converges.) - Jonathan Sondow, Mar 25 2014

References

  • Calvin C. Clawson, "Mathematical Mysteries, the beauty and magic of numbers," Perseus Books, Cambridge, Mass., 1996, pages 142 & 229.

Crossrefs

Programs

  • Mathematica
    f[n_] := Block[{k = n, s = 0}, While[k > 0, s = Sqrt[s + k]; k-- ]; s]; ContinuedFraction[ f[100], 101]; (* Robert G. Wilson v *)

Formula

Continued fraction expansion of sqrt(2 + sqrt(3 + sqrt(5 + sqrt(7 + sqrt(11 + ... + sqrt(prime(n))))).

Extensions

Offset changed by Andrew Howroyd, Aug 03 2024
Showing 1-10 of 28 results. Next