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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. 3
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

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Last modified February 26 11:03 EST 2020. Contains 332279 sequences. (Running on oeis4.)