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).

2, 6, 14, 46, 110, 366, 878, 2926, 19310, 52078, 314222, 1362798, 3459950, 11848558, 78957422, 615828334, 1689570158, 10279504750, 44639243118, 113358719854, 663114533742, 2862137789294, 20454323833710, 301929300544366, 1427829207386990, 3679629021072238

Offset: 1

Author

Alan Griffiths, Oct 08 2007

Keywords

• nonn

Examples

			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.
		

Crossrefs

Partial sums of A061285.

Programs

Python

import gmpy
a = gmpy.mpz(0)
i = 0
for p in range(3,100,2):
    if gmpy.is_prime(p):
        a = gmpy.setbit(a,(p-1)/2)
        i += 1
        print(i,a)

Formula

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