The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A175218 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A175218

The third nonprimes after the primes.
(history; published version)

#14 by Michael De Vlieger at Sun Oct 06 13:10:17 EDT 2024

STATUS

reviewed

approved

#13 by Joerg Arndt at Sun Oct 06 11:34:48 EDT 2024

STATUS

proposed

reviewed

#12 by Alois P. Heinz at Sun Oct 06 10:08:01 EDT 2024

STATUS

editing

proposed

#11 by Alois P. Heinz at Sun Oct 06 10:07:09 EDT 2024

CROSSREFS

Cf. A175216, A175217, A175219, A175220.

STATUS

proposed

editing

#10 by Stefano Spezia at Sun Oct 06 10:06:09 EDT 2024

STATUS

editing

proposed

#9 by Stefano Spezia at Sun Oct 06 10:05:57 EDT 2024

PROG

(PARI) a(n) = if(n<=2, 8, prime(n) + 2 + isprime(prime(n)+2) + 1) /* Georg Fischer, Oct 06 2024 */

STATUS

proposed

editing

#8 by Georg Fischer at Sun Oct 06 09:50:34 EDT 2024

STATUS

editing

proposed

#7 by Georg Fischer at Sun Oct 06 09:50:25 EDT 2024

PROG

(PARI) if(n<=2, 8, prime(n) + 2 + isprime(prime(n)+2) + 1) /* Georg Fischer, Oct 06 2024 */

EXTENSIONS

a(49) , a(52) and a(57) corrected by Georg Fischer, Oct 06 2024

#6 by Georg Fischer at Sun Oct 06 09:45:57 EDT 2024

DATA

8, 8, 9, 10, 15, 16, 21, 22, 26, 33, 34, 40, 45, 46, 50, 56, 63, 64, 70, 75, 76, 82, 86, 92, 100, 105, 106, 111, 112, 116, 130, 134, 141, 142, 153, 154, 160, 166, 170, 176, 183, 184, 195, 196, 201, 202, 214, 226, 230, 231, 232, 236, 242, 243, 244, 254, 260, 266, 272, 273, 274

FORMULA

For n>2: a(n) = A000040(n) + 2 + A010051(A000040(n) + 2) + 1. - Reinhard Zumkeller, Mar 29 2010 [corrected by _Georg Fischer_, Oct 06 2024]

EXAMPLE

prime(49) = 227, prime(50) = 229, therefore (228=1st, 230=2nd nonprime), 231 = a(49). - Georg Fischer, Oct 06 2024

PROG

(PARI) if(n<=2, 8, prime(n)+2+isprime(prime(n)+2)+1) /* Georg Fischer, Oct 06 2024 */

EXTENSIONS

a(49) corrected by Georg Fischer, Oct 06 2024

STATUS

approved

editing

#5 by Jon E. Schoenfield at Mon Jun 19 00:22:50 EDT 2017

STATUS

editing

approved