A393800 - OEIS

A393800

Decimal expansion of sqrt(5*sqrt(5) - 11)/2.

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

(list; constant; graph; refs; listen; history; text; internal format)

OFFSET

0,1

COMMENTS

This constant gives the asymptotic correlation between the number of hairpins and that of basepairs in an RNA secondary structure on a number of vertices tending to infinity (see Theorem 3 in Bu, Kauers, and Zeilberger).

LINKS

Table of n, a(n) for n=0..99.

AJ Bu, Manuel Kauers, and Doron Zeilberger, Statistical Analysis of Hairpins and BasePairs in RNA Secondary Structures, arXiv:2602.19255 [math.CO], 2026.

Index entries for algebraic numbers, degree 4.

FORMULA

Minimal polynomial: 4*x^4 + 22*x^2 - 1.

Equals sqrt(10*A134944 - 4). - Hugo Pfoertner, Feb 28 2026

EXAMPLE

0.212332220528908707853482303983010682218343138181...

MATHEMATICA

RealDigits[Sqrt[5Sqrt[5]-11]/2, 10, 100][[1]]

PROG