The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A368241

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A368241

a(n) = n - prevprime(n) if n is prime, n + primepi(n) otherwise; a(2) = 2.
(history; published version)

#49 by Michael De Vlieger at Wed Jan 31 07:57:54 EST 2024

STATUS

reviewed

approved

#48 by Kevin Ryde at Wed Jan 31 00:53:38 EST 2024

STATUS

proposed

reviewed

#47 by Kevin Ryde at Wed Jan 31 00:52:04 EST 2024

STATUS

editing

proposed

#46 by Kevin Ryde at Wed Jan 31 00:48:33 EST 2024

FORMULA

a(n+1) = a(n) + pi(a(n)) isnonprime(a(n)), a(n+1) = a(n) - previousprime(a(n)) isprime(a(n)), a(2) = 2.

STATUS

proposed

editing

Discussion

Wed Jan 31

00:52

Kevin Ryde: Delete formula.  That's trying to be trajectory step as in A368196 (doesn't apply here).

#45 by Hendrik Kuipers at Sat Jan 13 05:04:29 EST 2024

STATUS

editing

proposed

Discussion

Sat Jan 13

05:24

Jon E. Schoenfield: I’m sorry, I just now saw your question of Dec 29. (I’m also sorry that I don’t know the answer.)  :-(

07:54

Michel Marcus: I do not understand how this formula should be read

07:55

Michel Marcus: a(n+1) = a(n) + pi(a(n)) isnonprime(a(n)) : what does this mean ?

#44 by Hendrik Kuipers at Sat Jan 13 05:04:21 EST 2024

FORMULA

a(n+1) = a(n) + pi(a(n)) isnonprime(a(n)), a(n+1) = a(n) - previousprime(a(n)) isprime(a(n)), a(2) = 2.

STATUS

proposed

editing

#43 by Jon E. Schoenfield at Thu Dec 21 04:19:38 EST 2023

STATUS

editing

proposed

Discussion

Thu Dec 21

04:33

Hendrik Kuipers: @04:19 Jon E. Schoenfield yes

Fri Dec 22

04:41

Hendrik Kuipers: What are next steps towards publication?

Fri Dec 29

05:05

Hendrik Kuipers: @Jon E. Schoenfield What can I do to advance this?

#42 by Jon E. Schoenfield at Thu Dec 21 04:19:11 EST 2023

COMMENTS

prevprime(n) = A151799(n) is the next largest prime < n.

STATUS

proposed

editing

Discussion

Thu Dec 21

04:19

Jon E. Schoenfield: Is this okay?

#41 by Kevin Ryde at Wed Dec 20 18:27:14 EST 2023

STATUS

editing

proposed

Discussion

Thu Dec 21

00:11

Jon E. Schoenfield: Maybe it’s because I’m accustomed to seeing functions named “PreviousPrime()” and “NextPrime()”, but I don’t like the wording in the sentence that includes “prevprime(n) … is the next prime …”

#40 by Kevin Ryde at Wed Dec 20 18:26:57 EST 2023

COMMENTS

a(n) = 2 iff n=2 or n is the larger prime of a twin prime pair (A077800A006512).

CROSSREFS

Cf. A000720, A005171, A010051, A077800, A006512, A095117, A151799.

KEYWORD

nonn,easy,changed

STATUS

proposed

editing