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%I #28 Oct 30 2018 10:31:02
%S 7,17,38,71,110,161,218,333,449,573,758,881,1010,1245,1563,1799,2043,
%T 2378,2591,2883,3278,3693,4316,4898,5201,5510,5831,6158,7175,8318,
%U 8973,9521,10355,11249,11853,12795,13610,14445,15483,16199,17285,18431,19010
%N (p*q - 1)/2 where p and q are consecutive odd primes.
%C Primes in this sequence: 7, 17, 71, 449, 881, 2591, ... - _Zak Seidov_, Jan 14 2013
%H Harvey P. Dale, <a href="/A102770/b102770.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = (prime(n + 1)*prime(n + 2) - 1)/2.
%F a(n) ~ 0.5 n^2/log^2 n. - _Charles R Greathouse IV_, Jan 14 2013
%F a(n) = A023515(n+2)/2. - _Jason Kimberley_, Oct 23 2015
%e a(1) = (3*5 - 1)/2 = 7.
%e a(2) = (5*7 - 1)/2 = 17.
%e a(3) = (7*11 - 1)/2 = 38.
%t Table[(Prime[n] Prime[n + 1] - 1)/2, {n, 2, 50}] (* _Alonso del Arte_, Jan 14 2013 *)
%t (Times@@#-1)/2&/@Partition[Prime[Range[2,50]],2,1] (* _Harvey P. Dale_, Apr 10 2015 *)
%o (PARI) a(n)=prime(n+1)*prime(n+2)\2 \\ _Charles R Greathouse IV_, Jan 14 2013
%Y Cf. A006094, A023515, A086870, A120876.
%K easy,nonn
%O 1,1
%A _W. Neville Holmes_, Feb 10 2005
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