A328359 - OEIS

%I #21 Sep 08 2022 08:46:24

%S 5,68,93,121,143,172,185,188,203,215,217,219,244,284,289,301,303,321,

%T 342,393,404,413,415,428,436,471,490,517,535,570,581,604,669,687,697,

%U 788,791,815,858,870,892,1014,1057,1079,1135,1137,1139,1147,1167,1205,1206,1208,1210,1255,1268,1276

%N Numbers k such that Omega(k - 2) = Omega(k) = Omega(k + 2) where Omega = A001222.

%H Harvey P. Dale, <a href="/A328359/b328359.txt">Table of n, a(n) for n = 1..1000</a>

%e 5 is a term because A001222(3) = A001222(5) = A001222(7) = 1;

%e 68 is a term because A001222(66) = A001222(68) = A001222(70) = 3;

%e 93 is a term because A001222(91) = A001222(93) = A001222(95) = 2.

%t Select[Range[10^4],PrimeOmega[#-2]==PrimeOmega[#]==PrimeOmega[#+2]&] (* _Metin Sariyar_, Oct 14 2019 *)

%t Flatten[Position[Partition[PrimeOmega[Range[2000]],5,1],_?(#[[1]]== #[[3]] == #[[5]]&),1,Heads->False]]+2 (* _Harvey P. Dale_, Nov 02 2021 *)

%o (Magma) [k: k in [4..1300]| forall{m:m in [-2,2]| &+[p[2]: p in Factorization(k+m)] eq &+[p[2]: p in Factorization(k)] }]; // _Marius A. Burtea_, Oct 15 2019

%Y Cf. A001222, A280382, A278311.

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Oct 14 2019