A090421 - OEIS

%I #21 Apr 21 2015 18:48:55

%S 2,3,5,7,10,11,13,14,15,17,19,21,22,23,29,30,31,37,41,42,43,45,46,47,

%T 53,54,55,58,59,61,62,63,67,70,71,73,78,79,81,83,85,86,87,89,90,91,93,

%U 94,95,97,101,103,107,109,111,113,115,117,118,119,122,123

%N Numbers that can be written in binary representation as concatenation of primes.

%C A090418(a(n)) > 0; complement of A090419.

%C Terms in the sequence cannot end in 00, 0010, 001010, etc., and thus a(n) > 3n/2 + O(log n). - _Charles R Greathouse IV_, Apr 21 2015

%H Reinhard Zumkeller, <a href="/A090421/b090421.txt">Table of n, a(n) for n = 1..10000</a>

%o (Haskell)

%o a090421 n = a090421_list !! (n-1)

%o a090421_list = filter ((> 0) . a090418) [1..]

%o -- _Reinhard Zumkeller_, Aug 06 2012

%o (PARI) is_A090421(n)={isprime(n) || if(bittest(n,0),for(k=2,#binary(n)-2,bittest(n,k-1) && isprime(n%2^k) && is_A090421(n>>k) && return(1)), bittest(n,1) && is_A090421(n>>2))} \\ _Charles R Greathouse IV_ and _M. F. Hasler_, Apr 21 2015

%Y Cf. A004676, A007088, A090422.

%Y Cf. A000040, A090420, and A090423 are subsequences.

%K nonn,base

%O 1,1

%A _Reinhard Zumkeller_, Nov 30 2003

%E Based on corrections in A090418, data recomputed by _Reinhard Zumkeller_, Aug 06 2012