A049051 Numbers k such that k through k+4 all have the same number of divisors.

11605, 12855, 13782, 19142, 21494, 28374, 28375, 40311, 42805, 50582, 55254, 60231, 60663, 79094, 87655, 90181, 90182, 95845, 99655, 103621, 109765, 115591, 120727, 121045, 122151, 122871, 142454, 142806, 152630, 157493, 157494, 171893

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Donovan Johnson)

Crossrefs

Cf. A000005, A006558, A019273, A039665, A119479.

Other runs of equidivisor numbers: A005237 (runs of 2), A005238 (runs of 3), A006601 (runs of 4), A049052 (runs of 6), A049053 (runs of 7).

Programs

Mathematica

Flatten[Position[Partition[DivisorSigma[0,Range[200000]],5,1],?(Length[ Union[#]] == 1&),{1},Heads->False]] (* _Harvey P. Dale, May 30 2014 *)
SequencePosition[DivisorSigma[0,Range[200000]],{x_,x_,x_,x_,x_}][[All,1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jul 03 2017 *)