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A257836 Numbers which are the product of at least two consecutive odd numbers > 1.

%I A257836 #4 May 12 2015 17:57:21
%S A257836 15,35,63,99,105,143,195,255,315,323,399,483,575,675,693,783,899,945,
%T A257836 1023,1155,1287,1295,1443,1599,1763,1935,2115,2145,2303,2499,2703,
%U A257836 2915,3135,3315,3363,3465,3599,3843,4095,4355,4623,4845,4899,5183,5475,5775,6083
%N A257836 Numbers which are the product of at least two consecutive odd numbers > 1.
%H A257836 Reinhard Zumkeller, <a href="/A257836/b257836.txt">Table of n, a(n) for n = 1..10000</a>
%e A257836 .     |       |   ----- Factorizations into ... --------------
%e A257836 .   n |  a(n) |   prime powers     |   consecutive odd numbers
%e A257836 . ----+-------+--------------------+--------------------------
%e A257836 .   1 |    15 |   3 * 5            |   3 * 5
%e A257836 .   2 |    35 |   5 * 7            |   5 * 7
%e A257836 .   3 |    63 |   3^2 * 7          |   7 * 9
%e A257836 .   4 |    99 |   3^2 * 11         |   9 * 11
%e A257836 .   5 |   105 |   3 * 5 * 7        |   3 * 5 * 7
%e A257836 .   6 |   143 |   11 * 13          |   11 * 13
%e A257836 .   7 |   195 |   3 * 5 * 13       |   13 * 15
%e A257836 .   8 |   255 |   3 * 5 * 17       |   15 * 17
%e A257836 .   9 |   315 |   3^2 * 5 * 7      |   5 * 7 * 9
%e A257836 .  10 |   323 |   17 * 19          |   17 * 19
%e A257836 .  11 |   399 |   3 * 7 * 19       |   19 * 21
%e A257836 .  12 |   483 |   3 * 7 * 23       |   21 * 23
%e A257836 .  13 |   575 |   5^2 * 23         |   23 * 25
%e A257836 .  14 |   675 |   3^3 * 5^2        |   25 * 27
%e A257836 .  15 |   693 |   3^2 * 7 * 11     |   7 * 9 * 11
%e A257836 .  16 |   783 |   3^3 * 29         |   27 * 29
%e A257836 .  17 |   899 |   29 * 31          |   29 * 31
%e A257836 .  18 |   945 |   3^3 * 5 * 7      |   3 * 5 * 7 * 9
%e A257836 .  19 |  1023 |   3 * 11 * 31      |   31 * 33
%e A257836 .  20 |  1155 |   3 * 5 * 7 * 11   |   33 * 35
%e A257836 .  21 |  1287 |   3^2 * 11 * 13    |   9 * 11 * 13
%e A257836 .  22 |  1295 |   5 * 7 * 37       |   35 * 37
%e A257836 .  23 |  1443 |   3 * 13 * 37      |   37 * 39
%e A257836 .  24 |  1599 |   3 * 13 * 41      |   39 * 41
%e A257836 .  25 |  1763 |   41 * 43          |   41 * 43
%e A257836 .  26 |  1935 |   3^2 * 5 * 43     |   43 * 45
%e A257836 .  27 |  2115 |   3^2 * 5 * 47     |   45 * 47
%e A257836 .  28 |  2145 |   3 * 5 * 11 * 13  |   11 * 13 * 15
%e A257836 .  29 |  2303 |   7^2 * 47         |   47 * 49
%e A257836 .  30 |  2499 |   3 * 7^2 * 17     |   49 * 51  .
%o A257836 (Haskell)
%o A257836 import Data.Set (singleton, deleteFindMin, insert)
%o A257836 a257836 n = a257836_list !! (n-1)
%o A257836 a257836_list = f $ singleton (15, 3, 5) where
%o A257836    f s = y : f (insert (w, u, v') $ insert (w `div` u, u + 2, v') s')
%o A257836          where w = y * v'; v' = v + 2
%o A257836                ((y, u, v), s') = deleteFindMin s
%Y A257836 Cf. A005408, A097889.
%K A257836 nonn
%O A257836 1,1
%A A257836 _Reinhard Zumkeller_, May 12 2015