A376734 - OEIS

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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

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OFFSET

1,1

LINKS

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

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

PROG

(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)

CROSSREFS