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A005521 1 + (sum of first n odd primes - n)/2. 2

%I

%S 1,2,4,7,12,18,26,35,46,60,75,93,113,134,157,183,212,242,275,310,346,

%T 385,426,470,518,568,619,672,726,782,845,910,978,1047,1121,1196,1274,

%U 1355,1438,1524,1613,1703,1798

%N 1 + (sum of first n odd primes - n)/2.

%F a(n+1) = a(n) + (prime(n+1) - 1)/2 for odd primes prime(n+1).

%Y a(n+1) - 1 counts primorial intervals A065917. a(n+2) - 2*a(n+1) + a(n) = A028334(n). - _Frank Ellermann_

%K nonn

%O 0,2

%A _N. J. A. Sloane_.

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Last modified September 19 08:05 EDT 2021. Contains 347556 sequences. (Running on oeis4.)