A031157 Numbers that are both lucky and prime.

3, 7, 13, 31, 37, 43, 67, 73, 79, 127, 151, 163, 193, 211, 223, 241, 283, 307, 331, 349, 367, 409, 421, 433, 463, 487, 541, 577, 601, 613, 619, 631, 643, 673, 727, 739, 769, 787, 823, 883, 937, 991, 997, 1009, 1021, 1039, 1087, 1093, 1117, 1123

Offset: 1

Author

Patrick De Geest

Keywords

• nonn

Comments

A010051(a(n))*A145649(a(n)) = 1. - Reinhard Zumkeller, Oct 19 2008

Conjecture: This sequence is infinite. - Ahmad J. Masad, Feb 17 2020

Conjecture: If this sequence is infinite, then there exists a minimum sufficiently large integer k, such that for all a(n) > k, there exists a positive integer x and there exists m>n such that x(x-1) < a(n) < x^2 and x^2 < a(m) < x(x+1). This conjecture is similar to Oppermann's conjecture. - Ahmad J. Masad, Jun 23 2020

Links

• T. D. Noe, Table of n, a(n) for n = 1..10000
• Wikipedia, Lucky prime

Crossrefs

Cf. A000959, A055728.

Programs

Mathematica

luckies = Range[1, 1248, 2]; i = 2; While[ i <= (len = Length@luckies) && (k = luckies[[i]]) <= len, luckies = Drop[luckies, {k, len, k}]; i++ ]; Select[luckies, PrimeQ@# &] (* Robert G. Wilson v, May 12 2006 *)