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A089294 Smallest prime p_k such that n can be written as a "plus-minus" sum n=sum_(i=1..k)e_i*(p_i)^2 with distinct primes p_i<=p_k, where e_i is 1 or -1. 3

%I

%S 19,13,19,13,2,3,13,19,13,3,13,7,5,3,13,7,5,13,13,7,5,5,13,13,7,5,13,

%T 13,7,5,5,13,13,7,5,13,7,7,5,13,7,17,11,11,7,7,17,11,13,7,17,11,11,7,

%U 7,17,11,13,7,11,11,7,7,11,13,7,17,11,11,7,7,17,11,13,7,17,11,11,7,7,17,11

%N Smallest prime p_k such that n can be written as a "plus-minus" sum n=sum_(i=1..k)e_i*(p_i)^2 with distinct primes p_i<=p_k, where e_i is 1 or -1.

%C The first terms where this sequence differs from A088934 are n=22,31,52,87,89,98,118,127,...

%e a(22)=13 because 22 can be represented as -13^2+11^2+7^2+5^2-2^2.

%e The corresponding representation with the minimum number of terms is

%e 22=19^2-13^2-11^2-7^2 (A088934(22)=19, A088910(22)=4 terms)

%Y The positions of the records in this sequence are given in A089295. Cf. A088910, A088934.

%K nonn

%O 0,1

%A _W. Edwin Clark_ Nov 06 2003

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Last modified September 17 10:52 EDT 2019. Contains 327129 sequences. (Running on oeis4.)