cp's OEIS Frontend

A280023 Least k such that A002375(k) = A002375(k+n), or 0 if no such k exists.

%I A280023 #14 Feb 23 2017 23:27:19
%S A280023 1,4,3,5,5,8,7,8,5,9,5,7,13,5,11,12,11,13,12,11,23,18,17,10,9,8,7,18,
%T A280023 5,32,36,29,31,15,27,13,12,11,35,21,27,22,18,17,37,54,27,56,15,24,13,
%U A280023 12,11,60,21,30,37,18,17,56,30,32,105,39,39,58,27,48,55,24,53,85,33,39,71,30,39,130,42,45,100,45,56,85,66,42,105,36,45,109,33,54,70,30,51,98,39,65,67,39,57,97,51
%N A280023 Least k such that A002375(k) = A002375(k+n), or 0 if no such k exists.
%H A280023 Altug Alkan, <a href="/A280023/b280023.txt">Table of n, a(n) for n = 1..10000</a>
%e A280023 a(2) = 4 because smallest k such that A002375(k) = A002375(k+2) is 4; A002375(4) = A002375(6) = 1.
%o A280023 (PARI) a002375(n) = sum(i=2, primepi(n), isprime(2*n - prime(i)));
%o A280023 a(n) = my(k=1); while (a002375(n+k) != a002375(k), k++); k;
%Y A280023 Cf. A002375.
%K A280023 nonn
%O A280023 1,2
%A A280023 _Altug Alkan_, Feb 22 2017