OFFSET
1,1
COMMENTS
If there are odd perfect numbers n of the form n=k*(2*k-1) the corresponding k should appear in this sequence. The sequence has no even terms.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..700
EXAMPLE
For n=4, a(4) = 41 since n = 41*(82 -1) = 3321 and sigma(3321)= 5082 = 4*1270 +2.
MAPLE
with(numtheory): genz := proc(b)local z, n, s, d; for z from 1 to b by 2 do n := z*(2*z-1); s := sigma(n); if modp(n, 4)=2 then print(z); fi; od; end;
MATHEMATICA
Select[Range[1, 5001, 2], Mod[DivisorSigma[1, #(2#-1)], 4]==2&] (* Harvey P. Dale, Sep 30 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Luis H. Gallardo, May 26 2011
STATUS
approved