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a(n) is the denominator of the asymptotic density of numbers whose second smallest prime divisor (A119288) is prime(n).
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%I #8 Mar 14 2021 05:14:38

%S 1,6,10,15,1155,1365,12155,1616615,37182145,11849255,33426748355,

%T 247357937827,10141675450907,25652473199353,2928046583754721,

%U 155186468939000213,223317113839049087,558516101711461766587,796182527971658263007,241532826894674874877669,430046252763689411367557

%N a(n) is the denominator of the asymptotic density of numbers whose second smallest prime divisor (A119288) is prime(n).

%C See A342479 for details.

%H Amiram Eldar, <a href="/A342480/b342480.txt">Table of n, a(n) for n = 1..376</a>

%t f[n_] := Module[{p = Prime[n], q}, q = Select[Range[p - 1], PrimeQ]; Plus @@ (1/(q - 1))*Times @@ ((q - 1)/q)/p]; Denominator @ Array[f, 30]

%Y Cf. A038110, A038111, A119288, A342479 (numerators).

%K nonn,easy,frac

%O 1,2

%A _Amiram Eldar_, Mar 13 2021