A109227 Binary strings that have 1's where primes occur, 0's elsewhere and every term ends with the n-th prime index.

1, 11, 1101, 110101, 1101010001, 110101000101, 1101010001010001, 110101000101000101, 1101010001010001010001, 1101010001010001010001000001, 110101000101000101000100000101, 110101000101000101000100000101000001

Offset

1,2

Comments

a(2) and a(121) are primes. Are there any more?

Links

Amiram Eldar, Table of n, a(n) for n = 1..168

Example

a(4) = 110101 because the string '00110101' has 1's at the prime indices 2,3,5,7 and the first two zeros are dropped.

Mathematica

a[n_] := FromDigits[Boole @ PrimeQ[Range[Prime[n]]]]; Array[a, 12] (* Amiram Eldar, Aug 18 2020 *)

Crossrefs

Cf. A109228.

Sequence in context: A348269 A153435 A266787 * A133342 A110574 A280042

Adjacent sequences: A109224 A109225 A109226 * A109228 A109229 A109230

Keyword

base,easy,nonn

Author

Jason Earls, Jun 23 2005

Status

approved