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Variation on Ulam numbers: a(1) = 1; a(2) = 2; for n>2, a(n) = smallest (n odd) or largest (n even) number > a(n-1) that is a unique sum of two distinct earlier terms.

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`%I #6 Aug 09 2024 08:46:52
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`%S 1,2,3,5,6,11,12,23,24,47,48,95,96,191,192,383,384,767,768,1535,1536,
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`%T 3071,3072,6143,6144,12287,12288,24575,24576,49151,49152,98303,98304,
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`%U 196607,196608,393215,393216,786431,786432,1572863,1572864,3145727
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`%N Variation on Ulam numbers: a(1) = 1; a(2) = 2; for n>2, a(n) = smallest (n odd) or largest (n even) number > a(n-1) that is a unique sum of two distinct earlier terms.
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`%D Dan Asimov, post to math-fun mailing list, Feb 11, 2003.
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`%F Appears that a(2k) = 3*2^(k-1)-1, a(2k+1) = 3*2^(k-1) for k >= 1.
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`%Y Cf. A002858, A081025.
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`%K nonn
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`%O 1,2
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`%A _David W. Wilson_, Mar 02 2003
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