A133155 - OEIS

A133155

Numbers formed by setting bits representing odd primes, where bit_no = (prime - 1)/2. Setting bit number b is the same as OR-ing with 2^b (i.e., bit numbers start at zero).

%I #13 Dec 03 2024 19:53:38

%S 2,6,14,46,110,366,878,2926,19310,52078,314222,1362798,3459950,

%T 11848558,78957422,615828334,1689570158,10279504750,44639243118,

%U 113358719854,663114533742,2862137789294,20454323833710,301929300544366,1427829207386990,3679629021072238

%N Numbers formed by setting bits representing odd primes, where bit_no = (prime - 1)/2. Setting bit number b is the same as OR-ing with 2^b (i.e., bit numbers start at zero).

%F a(n) = setbit(a(n-1),(p-1)/2) where p is the n-th odd prime.

%e a(3) = 14 because 3, 5 and 7 are odd primes so therefore bits 1, 2 and 3 are set and bit zero is not. 1110_2 = 14.

%o (Python)

%o import gmpy

%o a = gmpy.mpz(0)

%o i = 0

%o for p in range(3,100,2):

%o if gmpy.is_prime(p):

%o a = gmpy.setbit(a,(p-1)/2)

%o i += 1

%o print(i,a)

%Y Partial sums of A061285.

%K nonn

%O 1,1

%A _Alan Griffiths_, Oct 08 2007