A093911 - OEIS

A093911

Left side of irregular triangle of natural numbers in which the n-th row has at least n terms and every row product is a multiple of the previous.

1, 2, 4, 7, 11, 17, 27, 47, 87, 167, 327, 635, 1263, 2519, 5007, 10007, 19947, 39875, 79739, 159399, 318779, 637503, 1274999, 2549979, 5099903, 10199787, 20399535, 40799063, 81598083, 163196135, 326392259, 652784499, 1305568943, 2611137839

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

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

EXAMPLE

The first 5 groups are (1), (2,3), (4,5,6), (7,8,9,10),

(11,12,13,14,15,16). The 5th group ends with 16 because

11*12*13*14*15*16 is divisible by 7*8*9*10, but 11*12*13*14*15 is not.

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. A090905, A093910, A093912, A093913.

Sequence in context: A023430 A023429 A023428 * A152398 A023427 A216116

Adjacent sequences: A093908 A093909 A093910 * A093912 A093913 A093914

KEYWORD

nonn,easy,less

AUTHOR

Amarnath Murthy, Apr 24 2004

EXTENSIONS

Edited and extended by David Wasserman, Mar 27 2006

STATUS

approved