A105548 Continued fraction expansion of prime nested radical A105546.

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

Author

Jonathan Vos Post, Apr 14 2005

Keywords

• cofr
• easy
• nonn

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.

Links

• Jonathan M. Borwein and G. de Barra, Nested Radicals, Amer. Math. Monthly 98, 735-739, 1991.
• J. Sondow and P. Hadjicostas, The generalized-Euler-constant function gamma(z) and a generalization of Somos's quadratic recurrence constant, J. Math. Anal. Appl., 332 (2007), 292-314; see pp. 305-306.
• Eric Weisstein's World of Mathematics, Nested Radical Constant.
• Wikipedia, Tirukkannapuram Vijayaraghavan

Crossrefs

Cf. A000040, A072449, A105546, A239349.

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