A174797 Numbers n such that both semiprime(n) and semiprime(n+1) are even.
1, 4, 21, 87, 120, 141, 142, 168, 188, 320, 363, 387, 434, 464, 496, 539, 593, 675, 721, 794, 810, 995, 1032, 1105, 1147, 1166, 1228, 1356, 1391, 1477, 1478, 1498, 1702, 1771, 1790, 1797, 1803, 1818, 1849, 1850, 1881, 1967, 2016, 2039, 2052, 2065, 2091
Offset: 1
Keywords
Examples
a(1)=1 because both semiprime(1)=4 and semiprime(2)=6 are even a(2)=4 because both semiprime(4)=10 and semiprime(5)=14 are even.
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..2000
Programs
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Mathematica
Flatten[Position[Partition[Select[Range[10000],PrimeOmega[#]==2&],2,1],?(EvenQ[First[#]]&&EvenQ[Last[#]]&),{1},Heads->False]] (* _Harvey P. Dale, Apr 19 2014 *)
Extensions
Edited and corrected by Ray Chandler, Apr 07 2010
Comments