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A335911
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Numbers of the form q*(2^k), where k >= 0 and q is either a Fermat prime or a Mersenne prime; Numbers k for which A335885(k) = 1.
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4
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3, 5, 6, 7, 10, 12, 14, 17, 20, 24, 28, 31, 34, 40, 48, 56, 62, 68, 80, 96, 112, 124, 127, 136, 160, 192, 224, 248, 254, 257, 272, 320, 384, 448, 496, 508, 514, 544, 640, 768, 896, 992, 1016, 1028, 1088, 1280, 1536, 1792, 1984, 2032, 2056, 2176, 2560, 3072, 3584, 3968, 4064, 4112, 4352, 5120, 6144, 7168, 7936, 8128, 8191
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OFFSET
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1,1
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COMMENTS
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Product of any two terms (whether distinct or not) can be found in A335912.
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LINKS
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PROG
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(PARI)
A335885(n) = { my(f=factor(n)); sum(k=1, #f~, if(2==f[k, 1], 0, f[k, 2]*(1+min(A335885(f[k, 1]-1), A335885(f[k, 1]+1))))); };
(PARI)
isA000668(n) = (isprime(n)&&!bitand(n, 1+n));
isA019434(n) = ((n>2)&&isprime(n)&&!bitand(n-2, n-1));
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CROSSREFS
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Cf. A141453 (after its initial 2, gives the primes present in this sequence).
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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