A376734 Numbers k such that 2*k-1 and 2*k+1 are products of exactly three distinct odd primes (A046389).

332, 655, 773, 943, 1007, 1018, 1033, 1046, 1117, 1172, 1277, 1333, 1358, 1369, 1424, 1622, 1667, 1783, 1810, 1828, 1865, 1907, 1928, 2008, 2216, 2252, 2293, 2348, 2404, 2447, 2473, 2518, 2567, 2608, 2645, 2698, 2711, 2726, 2797, 2898, 2942, 2972, 2978, 3031, 3048, 3049

Offset: 1

Author

Hugo Pfoertner, Oct 18 2024

Keywords

• nonn

Links

• Dominic McCarty, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A046389, A234099, A234102.

Programs

Maple

q:= k-> andmap(x-> map(i-> i[2], ifactors(x)[2])=[1$3], [2*k-1, 2*k+1]):
select(q, [$1..4000])[];  # Alois P. Heinz, Oct 18 2024

PARI

is_a046389(k) = k%2 && omega(k)==3 && bigomega(k)==3;
is_a376734(n) = is_a046389(2*n-1) && is_a046389(2*n+1)