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Search: id:A144715
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| 275, 431, 587, 1115, 1271, 2309, 2891, 3203, 3725, 4421, 4787, 5453, 6017, 6257, 6599, 6797, 7295, 7841, 8507, 8735, 8975, 9233, 9557, 9983, 10733, 11327, 11939, 12875, 13031, 13439, 14285, 15113, 15383, 15665, 16307, 17129, 17849, 18461
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OFFSET
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1,1
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COMMENT
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All terms are congruent to 5 modulo 6: A144325(n) and A144313(n) are each congruent to 5 and A144315(n) is congruent to 1.
None of the given terms have more than three distinct prime factors and most have only two. Several are primes.
The multiples of five are all fifth figurate numbers corresponding to polygons having a number of sides k = floor(a(n) / 10) + 2. 3725 = 5 * 5 * 149 is also the 50th pentagonal number. The rest are not figurates, except for 15113 = 7 * 17 * 127, which is the seventeenth 113-figurate number.
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CROSSREFS
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Cf. A144325, A144313, A144315, A000326
Sequence in context: A066127 A062377 A157489 this_sequence A063368 A028531 A028533
Adjacent sequences: A144712 A144713 A144714 this_sequence A144716 A144717 A144718
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KEYWORD
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easy,nonn
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AUTHOR
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Reikku Kulon (reikku(AT)gmail.com), Sep 19 2008
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