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A280729 (p-1)/2 + phi(p-1) as p runs through the odd primes.

%I A280729 #11 Sep 08 2022 08:46:18
%S A280729 2,4,5,9,10,16,15,21,26,23,30,36,33,45,50,57,46,53,59,60,63,81,84,80,
%T A280729 90,83,105,90,104,99,113,132,113,146,115,126,135,165,170,177,138,167,
%U A280729 160,182,159,153,183,225,186,228,215,184,225,256,261,266,207,226,236,233
%N A280729 (p-1)/2 + phi(p-1) as p runs through the odd primes.
%H A280729 Vincenzo Librandi, <a href="/A280729/b280729.txt">Table of n, a(n) for n = 1..1000</a>
%F A280729 a(n) = A098006(n)+2*A008330(n). - _R. J. Mathar_, Jan 10 2017
%p A280729 A280729 := proc(n)
%p A280729     local p;
%p A280729     p := ithprime(n+1) ;
%p A280729     (p-1)/2+numtheory[phi](p-1) ;
%p A280729 end proc: # _R. J. Mathar_, Jan 10 2017
%t A280729 Table[(n - 1)/2 + EulerPhi[n - 1], {n, Prime[Range[2, 100]]}]
%o A280729 (Magma) [(NthPrime(n)-1)/2+EulerPhi(NthPrime(n)-1): n in [2..100]];
%Y A280729 Cf. A098006.
%K A280729 nonn,easy
%O A280729 1,1
%A A280729 _Vincenzo Librandi_, Jan 10 2017