Not being a programmer I figured I could still solve this without a lot of brute force on my part:
I figured semi-primes will have 4 distinct factors (unless they are squares) and are rather numerous. So I used the OEIS:
and scanned for triples. The central numbers are 34, 86, 94, 142, 202
Searching this leads to
Numbers n such that d(n-1) = d(n) = d(n+1).
Interestingly, the first number on this sequence that would not be in the semiprimes sequence is 231
230 = 2*5*23
231 = 3*7*11
232 = 2^3*29
each has 8 divisors.
Posted by Jer
on 2014-04-18 12:58:37