OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
n=613,614,615,616 have 2,4,8,16 divisors respectively.
MATHEMATICA
d0[x_] :=DivisorSigma[0, x]; ta={{0}}; Do[g=n; s=d0[n]; s1=d0[n+1]; s2=d0[n+2]; s3=d0[n+3] If[Equal[s1, 2*s]&&Equal[s2, 4*s]&&Equal[s3, 8*s], ta=Append[ta, n]; Print[{n, s, s1, s2, s3}]], {n, 1, 1000000}]; {ta=Delete[ta, 1], g}
nd2Q[{a_, b_, c_, d_}]:={b, c, d}/a=={2, 4, 8}; Position[Partition[ DivisorSigma[ 0, Range[80000]], 4, 1], _?(nd2Q[#]&)]//Flatten (* Harvey P. Dale, Feb 25 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Nov 19 2004
STATUS
approved