A028815 a(n) = prime(n) + 1 (starting with 1).

2, 3, 4, 6, 8, 12, 14, 18, 20, 24, 30, 32, 38, 42, 44, 48, 54, 60, 62, 68, 72, 74, 80, 84, 90, 98, 102, 104, 108, 110, 114, 128, 132, 138, 140, 150, 152, 158, 164, 168, 174, 180, 182, 192, 194, 198, 200, 212, 224, 228, 230, 234, 240, 242, 252, 258, 264, 270, 272, 278, 282, 284

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Comments

n-th noncomposite (unit or prime) positive integer + 1.

The "0th prime" is defined to be 1 (a unit, formerly considered to be prime).

Links

• G. C. Greubel, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A000040, A006093, A008578, A008864.

Cf. A141130, A141132, A141133, A141136, A141138.

Programs

Magma

A028815:= func< n | n eq 0 select 2 else 1 + NthPrime(n) >;
[A028815(n): n in [0..70]]; // G. C. Greubel, Aug 05 2024

Mathematica

Join[{2},Prime[Range[70]]+1] (* Harvey P. Dale, Oct 14 2019 *)

PARI

a(n) = if(n==0, 2, prime(n) + 1); \\ Altug Alkan, Mar 14 2018

SageMath

def A028815(n): return 2 if n==0 else 1+nth_prime(n)
[A028815(n) for n in range(71)] # G. C. Greubel, Aug 05 2024

Formula

a(n) = prime(n) + 1 = A000040(n) + 1 = A008864(n) for n >= 1.

a(n) = A008578(n+1) + 1, n >= 0.

a(n) = 2*A006254(n-1), for n >= 2, with a(0) = 2, a(1) = 3. - G. C. Greubel, Aug 05 2024