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A255173 Numbers n such that 1+prime(n) and 1+prime(n+1) are the product of the same number of primes. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 5 03:59 EST 2021. Contains 349530 sequences. (Running on oeis4.)