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%I #4 Jun 05 2015 13:00:01
%S 2,5,11,19,29,43,47,59,71,83,101,109,127,137,149,151,163,167,179,191,
%T 197,199,229,239,257,269,281,283,313,331,353,367,383,397,401,419,431,
%U 443,463,487,503,521,541,557,571,587,599,601,617,619,643,647,659,683
%N Numbers prime(k) such that D(prime(k), 3) < 0, where D( * , 3) = 3rd difference.
%C Partition of the positive integers: A064149, A258027, A258028;
%C Corresponding partition of the primes: A258029, A258030, A258031.
%H Clark Kimberling, <a href="/A258031/b258031.txt">Table of n, a(n) for n = 1..1000</a>
%F D(prime(k), 3) = P(k+3) - 3*P(k+2) + 3*P(k+1) - P(k), where P(m) = prime(m) for m >= 1.
%e D(prime(1), 3) = 7 - 3*5 + 3*3 - 2 < 0, so a(1) = prime(1) = 2;
%e D(prime(2), 3) = 11 - 3*7 + 3*5 - 3 > 0;
%e D(prime(3), 3) = 13 - 3*11 + 3*7 - 5 < 0, so a(2) = prime(3) = 5;
%e D(prime(4), 3) = 17 - 3*13 + 3*11 - 7 > 0
%t d = Differences[Table[Prime[n], {n, 1, 400}], 3];
%t u1 = Flatten[Position[d, 0]] (* A064149 *)
%t u2 = Flatten[Position[Sign[d], 1]] (* A258027 *)
%t u3 = Flatten[Position[Sign[d], -1]] (* A258028 *)
%t p1 = Prime[u1] (* A258029 *)
%t p2 = Prime[u2] (* A258030 *)
%t p3 = Prime[u3] (* A258031 *)
%Y Cf. A064149, A258027, A258028, A258029, A258030.
%K nonn,easy
%O 1,1
%A _Clark Kimberling_, Jun 05 2015
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