OFFSET
2,2
COMMENTS
Conjecture: a(n) exists for any n > 1.
LINKS
Hiroaki Yamanouchi, Table of n, a(n) for n = 2..53
Zhi-Wei Sun, A new theorem on the prime-counting function, arXiv:1409.5685, 2014.
EXAMPLE
a(3) = 2 since pi(3*2) = 3 = sigma(2), and pi(3*1) = 2 > sigma(1) = 1.
MATHEMATICA
Do[m=1; Label[aa]; If[PrimePi[n*m]==DivisorSigma[1, m], Print[n, " ", m]; Goto[bb]]; m=m+1; Goto[aa];
Label[bb]; Continue, {n, 2, 30}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, Sep 21 2014
EXTENSIONS
a(31)-a(42) from Hiroaki Yamanouchi, Oct 04 2014
STATUS
approved