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A144715 A144325(n) + A144313(n) + A144315(n) 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
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.
LINKS
CROSSREFS
Sequence in context: A066127 A062377 A157489 * A321487 A250736 A063368
KEYWORD
easy,nonn
AUTHOR
Reikku Kulon, Sep 19 2008
STATUS
approved

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Last modified April 23 11:19 EDT 2024. Contains 371912 sequences. (Running on oeis4.)