This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A242950 #7 May 28 2014 02:36:20 %S A242950 0,0,0,0,1,1,0,1,3,2,1,1,3,4,4,1,3,5,4,4,4,3,3,3,3,4,4,4,3,5,2,5,3,5, %T A242950 3,6,3,7,4,6,5,7,5,9,7,6,4,6,5,9,5,6,8,7,8,5,8,5,8,4,8,6,7,4,7,4,6,4, %U A242950 5,4,8,2,3,4,5,4,5,6,7,7 %N A242950 Number of ordered ways to write n = k + m with k > 1 and m > 1 such that the least nonnegative residue of prime(k) modulo k is a square and the least nonnegative residue of prime(m) modulo m is a prime. %C A242950 Conjecture: (i) a(n) > 0 for all n > 7. %C A242950 (ii) Any integer n > 9 can be written as k + m with k > 1 and m > 1 such that the least nonnegative residue of prime(k) modulo k and the least nonnegative residue of prime(m) modulo m are both prime. %C A242950 We have verified a(n) > 0 for all n = 8, ..., 10^8. %H A242950 Zhi-Wei Sun, <a href="/A242950/b242950.txt">Table of n, a(n) for n = 1..10000</a> %e A242950 a(11) = 1 since 11 = 2 + 9, prime(2) = 3 == 1^2 (mod 2), and prime(9) = 23 == 5 (mod 9) with 5 prime. %e A242950 a(16) = 1 since 16 = 12 + 4, prime(12) = 37 == 1^2 (mod 12), and prime(4) = 7 == 3 (mod 4) with 3 prime. %t A242950 SQ[n_]:=IntegerQ[Sqrt[n]] %t A242950 s[k_]:=SQ[Mod[Prime[k],k]] %t A242950 p[k_]:=PrimeQ[Mod[Prime[k],k]] %t A242950 a[n_]:=Sum[Boole[s[k]&&p[n-k]],{k,2,n-2}] %t A242950 Table[a[n],{n,1,80}] %Y A242950 Cf. A000290, A000040, A242425, A242748, A242753. %K A242950 nonn %O A242950 1,9 %A A242950 _Zhi-Wei Sun_, May 27 2014