A093912 Number of terms in n-th row of irregular triangle defined in A093911.

1, 2, 3, 4, 6, 10, 20, 40, 80, 160, 308, 628, 1256, 2488, 5000, 9940, 19928, 39864, 79660, 159380, 318724, 637496, 1274980, 2549924, 5099884, 10199748, 20399528, 40799020, 81598052, 163196124, 326392240, 652784444, 1305568896, 2611137796

Offset

1,2

Comments

First differences of A093911.

Links

Table of n, a(n) for n=1..34.

Example

From Michael De Vlieger, Dec 15 2016: (Start)
a(4) = 4 because a(1) is the product of 1 successive numbers starting with 1 = 1, a(2) is the product of 2 successive numbers (2,3) = 6, a(3) is the product of 3 successive numbers (4,5,6) = 120. Finally, a(4) is the product of 4 successive numbers (7,8,9,10) = 5040. All the products have the property that a(n) = 0 (mod a(n - 1)). Thus a(4) = 4. (End)

Mathematica

a = {{1, 1}, {2, 2}}; Do[k = Last@ a[[i]]; While[! Divisible[Pochhammer[Total@ a[[i]], k], Pochhammer @@ a[[i]]], k++]; AppendTo[a, {Total@ a[[i]], k}], {i, 2, 16}]; Last /@ a (* Michael De Vlieger, Dec 15 2016 *)

Crossrefs

Cf. A090906, A093911.

Sequence in context: A228863 A004047 A355191 * A181054 A134696 A151677

Adjacent sequences: A093909 A093910 A093911 * A093913 A093914 A093915

Keyword

nonn,easy,less

Author

Amarnath Murthy, Apr 24 2004

Extensions

Edited and extended by David Wasserman, Mar 27 2006

Status

approved