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a(1) = 1 and then group the prime numbers so that the n-th group contains n numbers with a composite sum: (1), (2, 7), (3, 5, 13), (11, 17, 19, 23), (29, 31, 37, 41, 47), (43, 53, 59, 61, 67, 71), ...

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`%I #4 Dec 05 2013 19:55:39
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`%S 1,2,7,3,5,13,11,17,19,23,29,31,37,41,47,43,53,59,61,67,71,73,79,83,
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`%T 89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,
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`%U 179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277
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`%N a(1) = 1 and then group the prime numbers so that the n-th group contains n numbers with a composite sum: (1), (2, 7), (3, 5, 13), (11, 17, 19, 23), (29, 31, 37, 41, 47), (43, 53, 59, 61, 67, 71), ...
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`%e 1; 2,7; 3,5,13; 11,17,19,23; 29,31,37,41,47; 43,53,59,61,67,71; ...
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`%Y Cf. A075640, A075641, A075642.
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`%K nonn,tabl
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`%O 1,2
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`%A _Amarnath Murthy_, Sep 30 2002
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`%E More terms from _David Wasserman_, Jan 22 2005
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