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a(n) = Omega(6*n-1)*Omega(6*n+1).
1

%I #7 Jul 16 2020 19:52:15

%S 1,1,1,2,1,2,1,2,2,1,2,1,2,2,2,2,1,1,2,4,3,2,1,4,1,2,2,2,3,1,4,1,1,4,

%T 2,4,2,1,2,1,6,2,2,2,1,3,1,4,2,4,2,1,2,6,2,2,6,1,2,2,2,2,2,3,2,2,2,2,

%U 4,1,6,1,2,2,2,3,1,2,6,2,2,2,2,2,2,4,1,4,4,3,2,4,2,2,1,3,4,2,3,1,3,2,1,8,2

%N a(n) = Omega(6*n-1)*Omega(6*n+1).

%e For n=1, Omega(6*n-1)*Omega(6*n+1)=Omega(5)*Omega(7)=1, so a(1)=1.

%p A172155 := proc(n) numtheory[bigomega](6*n-1)*numtheory[bigomega](6*n+1) ; end proc: seq(A172155(n),n=1..100) ; # _R. J. Mathar_, Jan 30 2010

%t Table[Times@@PrimeOmega[6*n+{1,-1}],{n,120}] (* _Harvey P. Dale_, Jul 16 2020 *)

%Y Cf. A145193.

%K nonn

%O 1,4

%A _Juri-Stepan Gerasimov_, Jan 26 2010

%E Corrected by _R. J. Mathar_, Jan 30 2010