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).

3, 5, 7, 29, 73, 2131, 4211

Offset

1,1

Comments

A072762(4211) tested as PRP, others certified primes

Links

Table of n, a(n) for n=1..7.

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 A358699 A322749

Adjacent sequences: A124074 A124075 A124076 * A124078 A124079 A124080

Keyword

hard,nonn

Author

Anton Vrba (antonvrba(AT)yahoo.com), Nov 24 2006

Status

approved