A244434 -id:A244434 - cp's OEIS frontend

A244433 a(n) is the smallest number m such that 2im+1 is composite for all i, 0

4, 12, 19, 19, 59, 92, 159, 159, 159, 227, 227, 256, 256, 256, 514, 514, 706, 706, 706, 706, 706, 706, 706, 1466, 1466, 1466, 1466, 1466, 1466, 5207, 5207, 5207, 5207, 5207, 5207, 5207, 5207, 5207, 5207, 5207, 5207, 21209, 21209, 21209, 21209, 21209, 21209, 21209, 21209, 21209, 21209, 21209, 21209, 62809, 62809, 62809, 86914, 86914, 86914, 152351

Offset: 1

Farideh Firoozbakht, Jul 18 2014

nonn

a(3)=a(4)=19, a(7)=a(8)=a(9)=159, ..., a(74)=a(75)=...=a(82)=424783, ... . A244434 gives numbers n such that a(n) does not belong to the set {a(n-1),a(n+1)}.

			a(3)=19 because all the three numbers 2*1*19+1=39, 2*2*19+1=77 & 2*3*19+1=115 are composite and 19 is the smallest such number.

Cf. A071576, A244434, A244435.

A244436 Numbers n such that A244435(n) is not in the set {A244435(n-1), A244435(n+1)}.

Original entry on oeis.org

4, 7, 13, 14, 21, 27, 28

Offset: 1

Farideh Firoozbakht, Jul 19 2014

			A244435(27)=6118 is not in the set {A244435(26), A244435(28)}={1667, 8249} also A244435(28)=8249 is not in the set {A244435(27), A244435(29)}={6118, 9098} so 27 and 28 are two terms of this sequence.

Cf. A244434, A244435.

cp's OEIS Frontend

A244433 a(n) is the smallest number m such that 2im+1 is composite for all i, 0

Views

Author

Keywords

Comments

Examples