|
%I #10 Nov 25 2015 20:52:47
%S 3,7,8,13,14,19,20,23,24,25,31,32,33,38,43,44,47,48,49,54,55,61,62,63,
%T 68,73,74,75,80,83,84,85,89,90,91,92,98,103,104,109,110,113,114,115,
%U 116,117,118,119,128,131,132,133,139,140,141,142,143,151,152,153,158
%N Numbers that are less than the average of their closest flanking primes.
%C Numbers that are nearer to the immediately previous prime than to the immediately next prime.
%C This sequence may be viewed as a generalization of A051635 (the weak primes) that includes qualifying composite numbers.
%C The union of this sequence with A264719 & A145025 is A000027 (omitting 1 & 2).
%H Chris Boyd, <a href="/A264720/b264720.txt">Table of n, a(n) for n = 1..10000</a>
%e a(11) = 31 because 31 < (29 + 37)/2 = 33.
%e a(12) = 32 because 32 < (31 + 37)/2 = 34.
%t Select[Range@ 162, # < (NextPrime[#, -1] + NextPrime@ #)/2 &] (* _Michael De Vlieger_, Nov 22 2015 *)
%o (PARI) test(n)= {if(n-precprime(n-1)<nextprime(n+1)-n&&n>2,return(1),return(0))}
%o for(i=1,200,if(test(i),print1(i,", ")))
%Y Cf. A051634, A145025, A264719, A264721, A264722.
%K nonn,easy
%O 1,1
%A _Chris Boyd_, Nov 21 2015
|
