OFFSET
5,1
COMMENTS
Conjecture: a(n) exists for every n = 5,6,...
LINKS
Zhi-Wei Sun and Hiroaki Yamanouchi, Table of n, a(n) for n = 5..52 (terms a(5)-a(40) from Zhi-Wei Sun)
Zhi-Wei Sun, A new theorem on the prime-counting function, arXiv:1409.5685, 2014.
EXAMPLE
a(5) = 18 since pi(5*18) = 24 = sigma(5+18).
MATHEMATICA
Do[m=1; Label[aa]; If[PrimePi[n*m]==DivisorSigma[1, m+n], Print[n, " ", m]; Goto[bb]]; m=m+1; Goto[aa];
Label[bb]; Continue, {n, 5, 40}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, Sep 21 2014
EXTENSIONS
a(41)-a(44) from Hiroaki Yamanouchi, Oct 04 2014
STATUS
approved