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a(n) = A000265(rad(prime(n)-1)), rad = A007947.
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%I #11 Aug 09 2022 10:56:35

%S 1,1,1,3,5,3,1,3,11,7,15,3,5,21,23,13,29,15,33,35,3,39,41,11,3,5,51,

%T 53,3,7,21,65,17,69,37,15,39,3,83,43,89,15,95,3,7,33,105,111,113,57,

%U 29,119,15,5,1,131,67,15,69,35,141,73,51,155,39,79,165,21,173,87,11,179

%N a(n) = A000265(rad(prime(n)-1)), rad = A007947.

%H Michael De Vlieger, <a href="/A356489/b356489.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A000265(rad(prime(n)-1)) = rad(A000265(prime(n)-1)).

%F a(n) = Product_{odd primes p dividing prime(n)-1} p.

%F a(n) = A000265(A077063(n)) = rad(A057023(n)) = A204455(prime(n)-1).

%e prime(8) = 19, so a(8) = A000265(rad(18)) = A000265(6) = 3.

%e prime(11) = 31, so a(11) = A000265(rad(30)) = A000265(30) = 15.

%t Array[#/2^IntegerExponent[#, 2] &[Times @@ FactorInteger[Prime[#] - 1][[All, 1]]] &, 72] (* _Michael De Vlieger_, Aug 09 2022 *)

%o (PARI) a(n) = factorback(setminus(factorint(prime(n)-1)[, 1]~, [2]))

%Y Cf. A000265, A007947, A077063, A057023, A204455.

%K nonn,easy

%O 1,4

%A _Jianing Song_, Aug 09 2022