A309065 - OEIS

%I #21 Jul 16 2019 11:51:12

%S 8,10,13,17,23,27,33,41,52,57,64,74,94,101,108,125,126,131,148,151,

%T 158,169,171,190,193,202,206,213,225,230,240,248,252,275,292,325,345,

%U 354,355,364,412,417,430,433,437,439,444,463,484,485,486,533,542,543,557,558,580,594

%N Numbers n such that A014574(n) can be represented as a product of two terms in A014574.

%F A307758(n) = A014574(a(n)).

%e A014574(8) = 72 = 4 * 18. 4 and 18 are both in A014574, so a(1) = 8.

%e A014574(10) = 108 = 6 * 18. 6 and 18 are both in A014574, so a(2) = 10.

%e A014574(13) = 180 = 6 * 30. 6 and 30 are both in A014574, so a(3) = 13.

%t divQ[s_, n_] := AnyTrue[s, MemberQ[s, #] && MemberQ[s, n/#] &]; tpmidQ[n_]:= AllTrue[n + {-1,1}, PrimeQ]; s={}; ind={}; c=0; Do[If[tpmidQ[n], c++; If[divQ[s,n], AppendTo[ind,c]]; AppendTo[s,n]], {n, 1, 10^5}]; ind (* _Amiram Eldar_, Jul 11 2019 *)

%Y Cf. A014574, A307758.

%K nonn

%O 1,1

%A _Dmitry Kamenetsky_, Jul 10 2019

%E More terms from _Jinyuan Wang_, Jul 11 2019