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A078324 Primes of the form m*rad(m)+1, where rad = A007947 (squarefree kernel). 5

%I #14 Jul 31 2022 07:45:59

%S 2,5,17,37,73,101,109,197,257,401,433,577,677,1153,1297,1373,1601,

%T 1801,2593,2917,3137,3457,3529,3889,4001,4357,5477,7057,8101,8713,

%U 8837,9001,10369,12101,13457,14401,15377,15877,16001,16901,17497,17957,18253,18433,20809

%N Primes of the form m*rad(m)+1, where rad = A007947 (squarefree kernel).

%H Reinhard Zumkeller, <a href="/A078324/b078324.txt">Table of n, a(n) for n = 1..1000</a>

%e 12*rad(12)+1 = 12*rad(3*2^2)+1 = 12*3*2+1 = 72+1 = 73, therefore 73 is a term.

%e a(33) = 10369 = 10368 + 1: A078310(1728) = (2*3)*(2^6*3^3) = 10368.

%t powQ[n_] := n == 1 || AllTrue[FactorInteger[n][[;; , 2]], # > 1 &]; Select[Prime[Range[2400]], powQ[# - 1] &] (* _Amiram Eldar_, Jul 31 2022 *)

%o (Haskell)

%o a078324 n = a078324_list !! (n-1)

%o a078324_list = filter ((== 1) . a010051') a224866_list

%o -- _Reinhard Zumkeller_, Jul 23 2013

%o (PARI) is(n) = isprime(n) && ispowerful(n-1); \\ _Amiram Eldar_, Jul 31 2022

%Y Intersection of A000040 and A224866.

%Y Cf. A010051, A078310, A078325.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Nov 23 2002

%E Missing terms 10369, 16001, 17497 and 18433 inserted by _Reinhard Zumkeller_, Jul 23 2013

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Last modified March 28 09:04 EDT 2024. Contains 371240 sequences. (Running on oeis4.)