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Search: id:A133155
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| A133155 |
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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). |
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+0
1
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| 2, 6, 14, 46, 110, 366, 878, 2926, 19310, 52078, 314222, 1362798, 3459950, 11848558, 78957422, 615828334, 1689570158, 10279504750, 44639243118, 113358719854, 663114533742, 2862137789294, 20454323833710, 301929300544366
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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a(n) = setbit(a(n-1),(p-1)/2) where p is n-th odd prime
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EXAMPLE
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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(base2) = 14(base10)
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PROGRAM
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#!/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
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CROSSREFS
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Sequence in context: A004066 A123383 A122109 this_sequence A011455 A055691 A072171
Adjacent sequences: A133152 A133153 A133154 this_sequence A133156 A133157 A133158
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KEYWORD
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nonn
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AUTHOR
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Alan Griffiths (a1an_g(AT)yahoo.co.uk), Oct 08 2007
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