A113525 Semiprimes in A056107.

4, 49, 301, 589, 973, 2353, 2701, 3073, 4333, 5293, 5809, 6349, 6913, 7501, 8749, 9409, 10801, 11533, 13069, 14701, 15553, 16429, 23233, 24301, 25393, 27649, 30001

Offset

1,1

Comments

Intersection of A056107 and A001358.

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Example

a(1) = 4 because A056107(1) = 3*1^2 + 1 = 4 = 2^2 is semiprime.
a(16) = 9409 because A056107(56) = 3*56^2 + 1 = 9409 = 97^2 is semiprime.
a(27) = 30001 because A056107(100) = 3*100^2 + 1 = 30001 = 19 * 1579 is semiprime.

Mathematica

Select[Array[3 #^2 + 1 &, 100], PrimeOmega[#] == 2 &] (* Michael De Vlieger, Mar 17 2021 *)

Crossrefs

Cf. A001358, A056107.

Cf. A113519, A113524, A113527, A113528, A113530.

Sequence in context: A100256 A163944 A000596 * A290263 A224538 A064751

Adjacent sequences: A113522 A113523 A113524 * A113526 A113527 A113528

Keyword

easy,nonn

Author

Jonathan Vos Post, Jan 12 2006

Status

approved