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 A124077 Indices of the primes in A072762; b(i=a(n)) is prime, b(i) coded as binary word of length=i with k-th bit set iff k is prime (1<=k<=i). 1
 3, 5, 7, 29, 73, 2131, 4211 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A072762(4211) tested as PRP, others certified primes LINKS EXAMPLE a(3)=7 as A072762(7)=53 and 53 is prime! Also, the binary concatenation of the first a(n) terms of A010051 is prime. E.g. the first 7 term concatenation is binary 0110101 = decimal 53 and is prime! MATHEMATICA F[j_] := PrimeQ[Numerator[ Sum[ 1/2^Prime[k], {k, 1, j} ] ]] ; Prime[Select[Range[600], F]] CROSSREFS Cf. A072762, A010051. Sequence in context: A098860 A106920 A060273 * A288891 A322749 A270269 Adjacent sequences:  A124074 A124075 A124076 * A124078 A124079 A124080 KEYWORD hard,nonn AUTHOR Anton Vrba (antonvrba(AT)yahoo.com), Nov 24 2006 STATUS approved

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Last modified September 18 09:05 EDT 2021. Contains 347518 sequences. (Running on oeis4.)