OFFSET
1,1
EXAMPLE
30 is a term since d(28) = 6, d(29) = 2, d(30) = 8, d(31) = 2, d(32) = 6 and 6 < 8 > 6, 2 < 8 > 2.
MATHEMATICA
SequencePosition[Table[DivisorSigma[0, n], {n, 1, 400}], {a_, b_, c_, d_, e_} /; Max[a, b, d, e] < c][[;; , 1]] + 2 (* Amiram Eldar, Jan 16 2024 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhicheng Wei, Jan 15 2024
STATUS
approved