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A109227
Binary strings that have 1's where primes occur, 0's elsewhere and every term ends with the n-th prime index.
2
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
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
KEYWORD
base,easy,nonn
AUTHOR
Jason Earls, Jun 23 2005
STATUS
approved