Sequence of 4 Consecutive Integers with Equal Number of Divisors

From ProofWiki
Jump to navigation Jump to search

Theorem

The following sequence of integers are sets of $4$ consecutive integers which all have the same number of divisors:

$\map {\sigma_0} m = \map {\sigma_0} {m + 1} = \map {\sigma_0} {m + 2} = \map {\sigma_0} {m + 3}$

where $\map {\sigma_0} n$ denotes the divisor count function.

$242, 243, 244, 245, 3655, 3656, 3657, 3658, 4503, 4504, 4505, 4506, \ldots$

This sequence is A039665 in the On-Line Encyclopedia of Integer Sequences (N. J. A. Sloane (Ed.), 2008).


Proof

\(\ds \map {\sigma_0} {242}\) \(=\) \(\ds 6\) $\sigma_0$ of $242$
\(\ds \map {\sigma_0} {243}\) \(=\) \(\ds 6\) $\sigma_0$ of $243$
\(\ds \map {\sigma_0} {244}\) \(=\) \(\ds 6\) $\sigma_0$ of $244$
\(\ds \map {\sigma_0} {245}\) \(=\) \(\ds 6\) $\sigma_0$ of $245$


\(\ds \map {\sigma_0} {3655}\) \(=\) \(\ds 8\) $\sigma_0$ of $3655$
\(\ds \map {\sigma_0} {3656}\) \(=\) \(\ds 8\) $\sigma_0$ of $3656$
\(\ds \map {\sigma_0} {3657}\) \(=\) \(\ds 8\) $\sigma_0$ of $3657$
\(\ds \map {\sigma_0} {3658}\) \(=\) \(\ds 8\) $\sigma_0$ of $3658$

$\blacksquare$


Sources