OFFSET
1,2
COMMENTS
Conjecture: a(n) exists for any n > 0.
LINKS
Zhi-Wei Sun, Table of n, a(n) for n = 1..10000
Zhi-Wei Sun, A new theorem on the prime-counting function, arXiv:1409.5685, 2014.
EXAMPLE
a(5) = 10 since 10 + 5 = 15 divides sigma(10)^2 + sigma(5)^2 = 18^2 + 6^2 = 360.
a(1024) = 2098177 since 2098177 + 1024 = 2099201 divides sigma(2098177)^2 + sigma(1024)^2 = 2103300^2 + 2047^2 = 4423875080209 = 2099201*2107409.
MATHEMATICA
Do[m=1; Label[aa]; If[Mod[DivisorSigma[1, m]^2+DivisorSigma[1, n]^2, m+n]==0, Print[n, " ", m]; Goto[bb]]; m=m+1; Goto[aa]; Label[bb]; Continue, {n, 1, 60}]
lpi[n_]:=Module[{m=1, dsn=DivisorSigma[1, n]^2}, While[ !Divisible[ DivisorSigma[ 1, m]^2+ dsn, m+n], m++]; m]; Array[lpi, 60] (* Harvey P. Dale, May 07 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, Sep 29 2014
STATUS
approved