A373810 a(n) is the smallest number of straight lines needed to intersect all points (k, phi(k)) for k = 1..n (where phi is the Euler totient function A000010).

1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 16, 16, 17

Offset: 1

Author

Rémy Sigrist and N. J. A. Sloane, Aug 18 2024

Keywords

• nonn

Links

• Max Alekseyev, Table of n, a(n) for n = 1..455
• Max Alekseyev, Sage program for lines covering points, Github, Aug 19 2024
• N. J. A. Sloane, A Nasty Surprise in a Sequence and Other OEIS Stories, Experimental Mathematics Seminar, Rutgers University, Oct 10 2024, Youtube video; Slides [Mentions this sequence]

Crossrefs

Cf. A000010, A375499, A373813, A373815 (RUNS).

Extensions

Terms a(19) onward from Max Alekseyev, Aug 18 2024