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A162317
A positive integer k is included if |d(k+1) - d(k)| is a prime, where d(k) is the number of divisors of k.
1
5, 6, 7, 10, 13, 16, 20, 22, 24, 27, 32, 35, 36, 37, 45, 46, 48, 49, 50, 51, 58, 61, 62, 64, 68, 73, 74, 76, 80, 82, 91, 92, 99, 100, 106, 115, 117, 120, 123, 124, 143, 144, 146, 152, 153, 157, 164, 166, 168, 169, 170, 174, 178, 187, 188, 193, 196, 206, 212, 224, 225
OFFSET
1,1
LINKS
EXAMPLE
24 is in the sequence because |d(25) - d(24)| = |3 - 8| = 5 is a prime. - Emeric Deutsch, Jul 12 2009
MAPLE
with(numtheory): a := proc (n) if isprime(abs(tau(n+1)-tau(n))) = true then n else end if end proc: seq(a(n), n = 1 .. 250); # Emeric Deutsch, Jul 12 2009
MATHEMATICA
Flatten[Position[Partition[DivisorSigma[0, Range[250]], 2, 1], _?(PrimeQ[Abs[ First[#]-Last[#]]]&), {1}, Heads->False]] (* Harvey P. Dale, May 26 2014 *)
CROSSREFS
Cf. A051950.
Sequence in context: A257604 A177089 A206415 * A162318 A350593 A108910
KEYWORD
nonn
AUTHOR
Leroy Quet, Jul 01 2009
EXTENSIONS
Extended by Emeric Deutsch, Jul 12 2009
STATUS
approved