OFFSET
1,2
COMMENTS
Conjecture: (i) a(n) exists for any n > 0.
(ii) For each integer m > 0, there is a positive integer n such that m + n divides prime(m^2) + prime(n^2).
LINKS
Zhi-Wei Sun, Table of n, a(n) for n = 1..1000
Zhi-Wei Sun, A new theorem on the prime-counting function, arXiv:1409.5685, 2014.
EXAMPLE
a(4) = 8 since 8 + 4 = 12 divides pi(8^2) + pi(4^2) = 18 + 6 = 24.
MATHEMATICA
Do[m=1; Label[aa]; If[Mod[PrimePi[m^2]+PrimePi[n^2], m+n]==0, Print[n, " ", m]; Goto[bb]]; m=m+1; Goto[aa]; Label[bb]; Continue, {n, 1, 70}]
a[ n_] := If[ n<1, 0, Module[ {m=1}, While[ Not @ Divisible[ PrimePi[m^2] + PrimePi[n^2], m + n], m++]; m]]; (* Michael Somos, Sep 30 2014 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, Sep 30 2014
STATUS
approved