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A346393
Irregular triangle read by rows: the n-th row gives the divisors of n ending with the final digit of n.
1
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1, 11, 2, 12, 13, 14, 5, 15, 16, 17, 18, 19, 10, 20, 1, 21, 2, 22, 23, 4, 24, 5, 25, 26, 27, 28, 29, 10, 30, 1, 31, 2, 32, 3, 33, 34, 5, 35, 6, 36, 37, 38, 39, 10, 20, 40, 1, 41, 2, 42, 43, 4, 44, 5, 15, 45, 46, 47, 8, 48, 49, 10, 50
OFFSET
1,2
EXAMPLE
The triangle begins:
1
2
3
4
5
6
7
8
9
10
1 11
2 12
13
14
5 15
16
17
18
19
10 20
1 21
2 22
23
4 24
5 25
26
27
28
29
10 30
1 31
2 32
3 33
34
5 35
6 36
37
38
39
10 20 40
...
MATHEMATICA
r[n_]:=Drop[Select[Divisors[n], (Mod[#, 10]==Mod[n, 10]&)]]; Flatten[Array[r, 50]]
PROG
(Python)
from sympy import divisors
def auptorow(nn):
for n in range(1, nn+1):
yield from [d for d in divisors(n) if d%10 == n%10]
print([an for an in auptorow(50)]) # Michael S. Branicky, Jul 21 2021
(PARI) row(n) = select(x->(x%10) == (n%10), divisors(n)); \\ Michel Marcus, Jul 25 2021
CROSSREFS
Cf. A010879, A027750, A330348 (row length).
Sequence in context: A067453 A203814 A373211 * A360074 A280505 A375968
KEYWORD
nonn,tabf,base
AUTHOR
Stefano Spezia, Jul 21 2021
STATUS
approved