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Primes in A065387 in the order of their appearance.
5

%I #29 Jan 22 2025 12:42:31

%S 2,19,19,79,103,113,257,523,509,1151,1279,1193,1579,2273,3061,2389,

%T 2693,2843,5003,4831,5119,7411,5693,5623,8623,6323,10139,8933,18401,

%U 14957,20411,20479,21191,20123,29683,28211,36833,55021,57203,68743,48761,66533,62423

%N Primes in A065387 in the order of their appearance.

%H Amiram Eldar, <a href="/A229264/b229264.txt">Table of n, a(n) for n = 1..1000</a>

%e Third term of A038344 is 9 and sigma(9) + phi(9) = 13 + 6 = 19 is prime.

%p with(numtheory); P:=proc(q) local a, n; for n from 1 to q do a:=sigma(n)+phi(n);

%p if isprime(a) then print(a); fi; od; end: P(10^6);

%t Select[Table[DivisorSigma[1,n]+EulerPhi[n],{n,30000}],PrimeQ] (* _Harvey P. Dale_, Apr 30 2018 *)

%o (PARI) lista(kmax) = {my(f, s); for(k = 1, kmax, f = factor(k); s= sigma(f) + eulerphi(f); if(isprime(s), print1(s, ", ")));} \\ _Amiram Eldar_, Nov 19 2024

%Y Cf. A000005, A000010, A000203, A009087, A023194, A038344, A055813, A062700, A064205, A065387, A115919, A141242, A229265, A229266, A229267, A229268.

%K nonn

%O 1,1

%A _Paolo P. Lava_, Sep 18 2013

%E Name corrected by _Amiram Eldar_, Nov 19 2024