The On-Line Encyclopedia of Integer Sequences (OEIS)

A175218 revision #9

A175218

The third nonprimes after the primes.

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, 231, 232, 236, 243, 244, 254, 260, 266, 273, 274

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OFFSET

1,1

LINKS

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

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

CROSSREFS