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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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified November 26 03:33 EST 2022. Contains 358353 sequences. (Running on oeis4.)