A382546 Positive integers whose prime factors are all in A219528.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 42, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 60, 62, 63, 64, 65, 66, 68, 69, 70, 71, 72, 73, 74, 75

Offset: 1

Author

Steven Lu, Mar 31 2025

Keywords

• nonn

Links

• Steven Lu, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A219528.

Programs

Mathematica

Select[Range[75], And @@ Table[SubsetQ[{2, 3}, First /@ FactorInteger[p + 1]] || SubsetQ[{2, 3}, First /@ FactorInteger[p - 1]], {p, First /@ FactorInteger[#]}] &]

Formula

Sum_{n>=1} 1/a(n) = 1/Product_{p in A219528} (1-1/p) = 7.52982574262479641306... . - Amiram Eldar, Apr 14 2025