A143545 a(n) = n unless n is a prime, in which case a(n) = 2n.

1, 4, 6, 4, 10, 6, 14, 8, 9, 10, 22, 12, 26, 14, 15, 16, 34, 18, 38, 20, 21, 22, 46, 24, 25, 26, 27, 28, 58, 30, 62, 32, 33, 34, 35, 36, 74, 38, 39, 40, 82, 42, 86, 44, 45, 46, 94, 48, 49, 50, 51, 52, 106, 54, 55, 56, 57, 58, 118, 60, 122, 62, 63, 64, 65, 66, 134, 68, 69, 70, 142

Offset

1,2

Links

N. J. A. Sloane, Table of n, a(n) for n = 1..10000

Formula

a(n) = n + A061397(n), where A061397 = (0, 2, 3, 0, 5, 0, 7,...).

Equals row sums of triangle A143544.

a(n)=A066560(n), n>1. [From R. J. Mathar, Sep 05 2008]

Example

a(3) = 6 = 2*3 since 3 is prime.
a(4) = 4 since 4 is a nonprime.

Crossrefs

Cf. A066560, A143544, A061397.

See A282028 for another version.

Sequence in context: A114595 A256415 A349093 * A338155 A328045 A277278

Adjacent sequences: A143542 A143543 A143544 * A143546 A143547 A143548

Keyword

nonn

Author

Gary W. Adamson, Aug 23 2008

Extensions

Extended beyond a(14) by R. J. Mathar, Sep 05 2008

Status

approved