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a(n) = (prime(n)-1)*(prime(n)-5)/12.
2

%I #16 Aug 13 2023 14:49:19

%S 0,1,5,8,16,21,33,56,65,96,120,133,161,208,261,280,341,385,408,481,

%T 533,616,736,800,833,901,936,1008,1281,1365,1496,1541,1776,1825,1976,

%U 2133,2241,2408,2581,2640,2945,3008,3136,3201,3605,4033,4181,4256,4408,4641

%N a(n) = (prime(n)-1)*(prime(n)-5)/12.

%C Confirmed a(n) = A242090(n) for 3 <= n <= 4000. - _Fausto A. C. Cariboni_, Feb 23 2019

%H T. D. Noe, <a href="/A030006/b030006.txt">Table of n, a(n) for n = 3..1000</a>

%t Table[(p - 1) (p - 5)/12, {p, Prime[Range[3, 50]]}] (* _T. D. Noe_, Apr 16 2012 *)

%t ((#-1)(#-5))/12&/@Prime[Range[3,60]] (* _Harvey P. Dale_, Aug 13 2023 *)

%Y Cf. A000040.

%K nonn

%O 3,3

%A _N. J. A. Sloane_.