login
a(n) is the least triprime k such that k + n is the next triprime after k.
1

%I #11 Mar 14 2024 15:21:43

%S 27,18,63,8,45,12,20,130,138,154,52,30,561,78,1194,1930,4277,292,5343,

%T 26353,4255,7847,34773,18628,71718,72308,168114,64699,43209,227451,

%U 239643,17641,97061,162124,924718,930311,488001,7248711,2986751,704908,4108654,7220012

%N a(n) is the least triprime k such that k + n is the next triprime after k.

%H Martin Raab, <a href="/A366673/b366673.txt">Table of n, a(n) for n = 1..83</a>

%e a(3) = 63 because 63 = 3^2 * 7 is a triprime and the next triprime is 63 + 3 = 66 = 2 * 3 * 11.

%p T:= select(t -> numtheory:-bigomega(t) = 3, [$1..10^7]):

%p dT:= T[2..-1]-T[1..-2]:

%p V:= Vector(42):

%p for i from 1 to nops(dT) do

%p if dT[i] <= 42 and V[dT[i]] = 0 then V[dT[i]]:= T[i] fi

%p od:

%p convert(V,list);

%Y Cf. A014612, A131109.

%K nonn

%O 1,1

%A _Zak Seidov_ and _Robert Israel_, Oct 16 2023