A330410 a(n) = 6*prime(n) - 1.

11, 17, 29, 41, 65, 77, 101, 113, 137, 173, 185, 221, 245, 257, 281, 317, 353, 365, 401, 425, 437, 473, 497, 533, 581, 605, 617, 641, 653, 677, 761, 785, 821, 833, 893, 905, 941, 977, 1001, 1037, 1073, 1085, 1145, 1157, 1181, 1193, 1265, 1337, 1361, 1373, 1397, 1433, 1445

Offset: 1

Author

M. F. Hasler, Dec 13 2019

Keywords

• nonn

Comments

Composite terms are a(k) with k in {5, 6, 11, 12, 13, 18, 20, 21, ...} = indices of primes missing in A158015. Primes are A016969(A158015 - 1).

Crossrefs

Cf. A000040 (primes), A016969 (6n+5), A024898 (6n-1 is prime), A158015 (primes in A024898), A049452 = {n(6n-1)}, A255584 = A033570(A130800) (semiprimes (2n+1)(3n+1)), A245365 (primes of the form n(3n-1)/2).

Programs

PARI

apply( a(n)=6*prime(n)-1, [1..99])

PARI

apply( n->6*n-1, primes(99))

Formula

a(n) = A016969(A000040(n)-1) = 6p - 1 with p = A000040(n) = prime(n).