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A189506 Irregular triangle read by rows in which row n (n >= 1) lists the base-10 lunar divisors of n. 1
1, 2, 3, 4, 5, 6, 7, 8, 9, 2, 3, 4, 5, 6, 7, 8, 9, 3, 4, 5, 6, 7, 8, 9, 4, 5, 6, 7, 8, 9, 5, 6, 7, 8, 9, 6, 7, 8, 9, 7, 8, 9, 8, 9, 9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
D. Applegate, M. LeBrun and N. J. A. Sloane, Dismal Arithmetic, arXiv:1107.1130 [math.NT], 2011. [Note: we have now changed the name from "dismal arithmetic" to "lunar arithmetic" - the old name was too depressing]
D. Applegate, M. LeBrun, N. J. A. Sloane, Dismal Arithmetic, J. Int. Seq. 14 (2011) # 11.9.8.
EXAMPLE
The first 11 rows give the divisors of 1 through 11:
1 2 3 4 5 6 7 8 9
2 3 4 5 6 7 8 9
3 4 5 6 7 8 9
4 5 6 7 8 9
5 6 7 8 9
6 7 8 9
7 8 9
8 9
9
1 2 3 4 5 6 7 8 9 10 20 30 40 50 60 70 80 90
1 2 3 4 5 6 7 8 9 11 12 13 14 15 16 17 18 19 21 22 23 24 25 26 27 28 29 31 32 33 34 35 36 37 38 39 41 ... 99 (= all zeroless 1- and 2-digit numbers).
PROG
(PARI) A189506_row(n)={my(d=digits(n), m=vecmin(d), c=vector(#d, i, List()), K, t); for(L=1, #d, K=#d-L+1; forvec(v=vector(L, i, [max(m, i==1), 9]), L<=K&& listput(c[L], fromdigits(v))&&next; t=fromdigits(v); forstep(i=#c[K], 1, -1, A087062(c[K][i], t)==n||next; listput(c[L], t); break)); L>=K&&forstep(i=#c[K], 1, -1, t=c[K][i]; forstep(j=#c[L], 1, -1, A087062(c[L][j], t)==n&&next(2)); listpop(c[K], i))); Set(concat(c))} \\ M. F. Hasler, Nov 15 2018
CROSSREFS
Cf. A087062 (lunar product).
Row n has A087029(n) terms.
Sequence in context: A238986 A227876 A276716 * A173529 A273005 A093017
KEYWORD
nonn,tabf
AUTHOR
N. J. A. Sloane, Apr 25 2011
EXTENSIONS
Minor edits by M. F. Hasler, Nov 15 2018
STATUS
approved

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Last modified May 23 17:39 EDT 2024. Contains 372765 sequences. (Running on oeis4.)