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A332740
Prime numbers p such that the set of composite numbers in the range [p+1, nextprime(p)-1] has more than one element and all the elements have the same number of divisors.
1
229, 8293, 9829, 14887, 16087, 20389, 21493, 44983, 50581, 53887, 57943, 63463, 64663, 72223, 81547, 93253, 108343, 134917, 138727, 143239, 157207, 192613, 199669, 203653, 206407, 210853, 218839, 244837, 248749, 251287, 255049, 262693, 280183, 296437, 300319
OFFSET
1,1
COMMENTS
The corresponding numbers of divisors are 8, 16, 8, 8, 8, 8, 8, 8, 8, 16, 8, 8, 16, 24, 24, ... and the number of divisors in the order of their first appearance are 8, 16, 24, 20, 12, 32, 48, ...
The number of composites between a(n) and its next prime are 3, 3, 3, 3, 3, 3, 5, 3, 5, 3, ... Are there terms with number of composites larger than 5?
LINKS
EXAMPLE
229 is a term since between 229 and its next prime, 233, there are 3 composite numbers, 230, 231 and 232 and all of them have the same number of divisors, 8.
MATHEMATICA
seqQ[n_] := PrimeQ[n] && (nx=NextPrime[n]) > n + 2 && Length @ Union @ DivisorSigma[0, Range[n+1, nx-1]] == 1; Select[Range[10^6], seqQ]
KEYWORD
nonn
AUTHOR
Amiram Eldar, Feb 21 2020
STATUS
approved