|
Search: id:A120712
|
|
|
| A120712 |
|
Numbers n with property that the concatenation of the proper divisors of n (i.e. excluding 1 and n) is a prime. |
|
+0
6
|
|
| 4, 6, 9, 21, 22, 25, 33, 39, 46, 49, 51, 54, 58, 78, 82, 93, 99, 111, 115, 121, 133, 141, 142, 147, 153, 154, 159, 162, 166, 169, 174, 177, 186, 187, 189, 201, 205, 219, 226, 235, 237, 247, 249, 253, 262, 267, 274, 286, 289, 291, 294, 301, 318
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
EXAMPLE
|
n -> divisors -> prime
----------------
4 -> 1,2,4 -> 2
6 -> 1,2,3,6 -> 23
9 -> 1,3,9 -> 3
21 -> 1,3,7,21 -> 37
22 -> 1,2,11,22 -> 211
25 -> 1,5,25 -> 5
33 -> 1,3,11,33 -> 311
39 -> 1,3,13,39 -> 313
|
|
MAPLE
|
Maple program from Simon Plouffe: with(numtheory):
for k from 2 to 1000 do:
v0:=divisors(k):
nn:=nops(v0):
if nn > 2 then
v1:=[seq(v0[j], j=2..nn-1)]:
v2:=cat(seq(convert(v1[n], string), n=1..nops(v1))):
v3:=parse(v2):
if isprime(v3) = true then lprint(k, v3) fi:
fi:
od:
|
|
CROSSREFS
|
Cf. A120716, A120713, A037274, A037278, A106708, A106736.
Cf. A130139-A130142.
Adjacent sequences: A120709 A120710 A120711 this_sequence A120713 A120714 A120715
Sequence in context: A036667 A056016 A098485 this_sequence A115698 A039566 A032817
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
Eric Angelini (Eric.Angelini(AT)kntv.be), Jul 19 2007
|
|
|
Search completed in 0.002 seconds
|
