A255173 Numbers n such that 1+prime(n) and 1+prime(n+1) are the product of the same number of primes.

2, 4, 7, 13, 16, 23, 25, 29, 34, 35, 56, 57, 60, 62, 66, 67, 69, 79, 90, 93, 97, 102, 103, 104, 107, 114, 121, 132, 136, 148, 159, 161, 187, 188, 193, 197, 208, 209, 212, 213, 224, 234, 243, 244, 248, 266, 276, 278, 313, 320, 325, 327, 331, 337, 338, 341, 343, 351

Offset

1,1

Comments

Number of primes counted with multiplicity. - Harvey P. Dale, Sep 05 2021

Links

Table of n, a(n) for n=1..58.

Example

2 is in the list since 1 + prime(2) = 4 and 1 + prime(3) = 6 are both products of 2 primes.
4 is in the list since 1 + prime(4) = 8 and 1 + prime(5) = 12 are both products of 3 primes.

Mathematica

Reap[Do[If[PrimeOmega[1 + Prime[n + 1]] == PrimeOmega[1 + Prime[n]], Sow[n]], {n, 200}]][[2, 1]]
SequencePosition[Table[PrimeOmega[Prime[n]+1], {n, 400}], {x_, x_}][[All, 1]] (* Harvey P. Dale, Sep 05 2021 *)

Crossrefs

Sequence in context: A018414 A002152 A163522 * A002466 A162842 A164901

Adjacent sequences: A255170 A255171 A255172 * A255174 A255175 A255176

Keyword

nonn

Author

Zak Seidov, Feb 15 2015

Status

approved