A370775 Integers m whose (constant) convergence speed is exactly 2 (i.e., m^^(m+1) has 2 more rightmost frozen digits than m^^m, where ^^ indicates tetration).

5, 7, 18, 24, 26, 32, 35, 43, 45, 49, 51, 74, 75, 76, 82, 85, 93, 99, 107, 115, 118, 125, 132, 143, 149, 151, 155, 157, 165, 168, 174, 176, 195, 199, 201, 205, 207, 218, 224, 226, 232, 235, 243, 245, 251, 257, 268, 274, 275, 276, 282, 285, 293, 299, 301, 307

Offset: 1

Author

Marco Ripà, May 01 2024

Keywords

• nonn
• base

Comments

It is well known (see Links) that as the hyperexponent of the integer m becomes sufficiently large, the constant convergence speed of m is the number of new stable digits that appear at the end of the result for any further unit increment of the hyperexponent itself, and a sufficient (but not necessary) condition to get this fixed value is to set the hyperexponent equal to m plus 1.

Examples

			If n = 2, m = 7 and so 7^^8 has exactly 2 more stable digits at the end of the result than 7^^7.
		

Links

• Marco Ripà, On the constant congruence speed of tetration, Notes on Number Theory and Discrete Mathematics, Volume 26, 2020, Number 3, Pages 245—260 (see Table 1, pp. 249—251).
• Marco Ripà and Luca Onnis, Number of stable digits of any integer tetration, Notes on Number Theory and Discrete Mathematics, 2022, 28(3), 441—457 (see Equation 16, p. 454).
• Wikipedia, Tetration

Crossrefs

Cf. A317905 (convergence speed of m^^m), A321130, A321131, A371129.

Formula

a(n) is such that A317905(m) = 2, for m = 5, 6, 7, ...