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A134189
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a(1)=1. Thereafter, a(n) = n*a(n-1) if the number of divisors of n*a(n-1) is <= the number of divisors of n+a(n-1) or a(n) = n+a(n-1) if n*a(n-1) has more divisors than n+a(n-1).
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1
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1, 2, 5, 9, 14, 20, 27, 35, 44, 54, 65, 77, 1001, 1015, 1030, 1046, 1063, 1081, 20539, 20559, 431739, 431761, 9930503, 9930527, 248263175, 248263201, 248263228, 248263256, 248263285, 248263315, 248263346, 248263378, 248263411, 8440955974, 8440956009
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OFFSET
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1,2
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LINKS
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EXAMPLE
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a(12)+13 = 77 + 13 = 90. a(12)*13 = 77 * 13 = 1001. 90 has 12 divisors. 1001 has 8 divisors. Since 1001 has fewer divisors than 90, a(13) is 1001.
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PROG
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(PARI) lista(nn) = {preca = 1; print1(preca, ", "); for (i = 2, nn, if (numdiv(p=i*preca) <= numdiv(s=i+preca), nexta = p, nexta = s); print1(nexta, ", "); preca = nexta; ); } \\ Michel Marcus, Feb 10 2014
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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