A362811 Sphenic numbers (product of 3 distinct primes) sandwiched between two semiprimes (product of 2 primes).
186, 266, 290, 322, 470, 518, 534, 582, 590, 670, 754, 790, 814, 894, 994, 1146, 1158, 1166, 1338, 1370, 1390, 1562, 1686, 1798, 1842, 1958, 2118, 2158, 2230, 2318, 2454, 2482, 2514, 2570, 2630, 2758, 2786, 2810, 2922, 2930, 2994, 3154, 3206, 3262, 3278, 3378, 3454, 3522, 3562
Offset: 1
Examples
186 is a term because 186=2*3*31, 185=5*37, 187=11*17.
Links
- Michael De Vlieger, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
Select[Range[2, 3600, 2], FactorInteger[#][[;; , 2]] == {1, 1, 1} && PrimeOmega[# - 1] == 2 && PrimeOmega[# + 1] == 2 &] (* Amiram Eldar, May 05 2023 *) -
PARI
isok(k)=omega(k)==3 && bigomega(k)==3 && bigomega(k-1)==2 && bigomega(k+1)==2
Comments