A088070 Numbers sandwiched between two numbers having the same number of prime divisors.

3, 4, 6, 8, 10, 11, 12, 13, 18, 19, 21, 23, 24, 25, 26, 27, 28, 30, 34, 35, 37, 39, 42, 45, 47, 48, 49, 51, 53, 55, 56, 57, 60, 64, 72, 73, 75, 76, 80, 81, 82, 86, 87, 92, 93, 94, 95, 97, 99, 102, 105, 107, 108, 116, 117, 118, 123, 126, 131, 134, 135, 138, 139, 142, 143, 144

Offset

1,1

Comments

Subsidiary sequence: (1) Start of the first run of a string of n successive integers in this sequence. Conjecture: For every k there is a string of k successive integers.

Links

Giovanni Resta, Table of n, a(n) for n = 1..10000

Formula

a(n) = A063464(n) + 1.

Example

11 is a member as 10 and 12 both have two prime divisors.
26 is a member as 25 and 27 both have one each prime divisor.

Prog

(PARI) isok(n) = omega(n-1) == omega(n+1); \\ Michel Marcus, Oct 18 2016

Crossrefs

Cf. A063464.

Sequence in context: A298809 A335194 A307647 * A175071 A336822 A140497

Adjacent sequences: A088067 A088068 A088069 * A088071 A088072 A088073

Keyword

nonn

Author

Amarnath Murthy, Sep 22 2003

Extensions

More terms from Ray Chandler, Sep 27 2003

Offset corrected and formula adapted by Michel Marcus, Oct 18 2016

Status

approved