A025017 a(n) = least 2k such that p is the least prime in a Goldbach partition of 2k, where p = prime(n).
4, 6, 12, 30, 124, 122, 418, 98, 220, 346, 308, 1274, 1144, 962, 556, 2512, 3526, 1382, 1856, 4618, 992, 3818, 7432, 12778, 5978, 26098, 2642, 23266, 10268, 19696, 6008, 34192, 22606, 5372, 37768, 13562, 9596, 22832, 59914, 7426, 88786, 50312, 97768
Offset: 1
Keywords
Examples
a(4)=30=7+23 because p(4)=7, q=23 is prime and there is no prime r<p(4)=7 such that a(4)-r is prime.
Links
- N. J. A. Sloane, Table of n, a(n) for n = 1..977 (from the web page of Tomás Oliveira e Silva)
- Tomás Oliveira e Silva, Goldbach conjecture verification
- Index entries for sequences related to Goldbach conjecture
Programs
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MATLAB
p1 = primes(1000000); d(1, :) = p1; d(2, :) = d(1, :) - d(1, :); i = 4; k = 1; n = 0; while i <= 5000000 while not(isprime(i - d(1, k))) k = k + 1; end; if d(2, k) == 0 d(2, k) = i; if k == n + 1 while d(2, n+1) > 0 n = n + 1; end; if n > 0 d(2, 1:n) end; end; end; k = 1; i = i + 2; end; - Lei Zhou, Jan 26 2005
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PARI
Gold(n)=forprime(p=2,n,if(isprime(n-p),return(p))) a(n,p=prime(n))=my(k=2); while(Gold(k+=2)!=p,); k \\ Charles R Greathouse IV, Sep 28 2015
Extensions
Edited by N. J. A. Sloane, May 05 2007; b-file added Nov 27 2007
Comments