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

1,1

Links

Table of n, a(n) for n=1..26.

Formula

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

Example

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.

Prog

#!/usr/bin/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

Crossrefs

Partial sums of A061285.

Sequence in context: A152806 A366223 A122109 * A297708 A284701 A011455

Adjacent sequences: A133152 A133153 A133154 * A133156 A133157 A133158

Keyword

nonn

Author

Alan Griffiths, Oct 08 2007

Status

approved