

A335398


Starts of runs of 4 consecutive numbers that have an equal number of unitary and nonunitary divisors (A048109).


2



2068373, 2948373, 3571749, 3916374, 4730373, 4757750, 6755750, 8109125, 11290872, 12248872, 13071750, 13648311, 13903623, 15278247, 15448374, 15449749, 16793622, 17446374, 17991125, 19407624, 20080248, 20250375, 21594248, 22577750, 24190758, 25297622, 26140373
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OFFSET

1,1


LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000


EXAMPLE

2068373 is a term since 2068373, 2068374, 2068375 and 2068376 each have an equal number of unitary and nonunitary divisors. 2068373 and 2068375 each have 4 unitary divisors and 4 nonunitary divisors, 2068374 has 32 unitary divisors and 32 nonunitary divisors, and 2068376 has 8 unitary divisors and 8 nonunitary divisors.


MATHEMATICA

q[n_] := DivisorSigma[0, n] == 2^(PrimeNu[n] + 1); v = q /@ Range[4]; seq = {}; Do[v = Append[Drop[v, 1], q[k]]; If[And @@ v, AppendTo[seq, k  3]], {k, 5, 10^7}]; seq


CROSSREFS

Subsequence of A048109, A335328 and A335397.
Cf. A000005, A034444, A048105.
Sequence in context: A186915 A186907 A186906 * A155125 A155126 A234469
Adjacent sequences: A335395 A335396 A335397 * A335399 A335400 A335401


KEYWORD

nonn


AUTHOR

Zak Seidov and Amiram Eldar, Jun 06 2020


STATUS

approved



