A272142 Numbers such that the concatenation of their aliquot parts, in descending order, are prime numbers.

8, 9, 10, 26, 34, 35, 49, 55, 56, 57, 62, 63, 75, 76, 77, 94, 95, 115, 122, 125, 142, 144, 146, 161, 169, 183, 194, 196, 203, 206, 219, 226, 235, 238, 254, 262, 265, 274, 275, 278, 290, 299, 302, 304, 305, 309, 320, 322, 332, 336, 338, 346, 355, 358, 361, 362

Offset: 1

Author

Paolo P. Lava, Apr 21 2016

Keywords

• nonn
• base
• easy

Examples

			Aliquot parts of 8 are 1, 2, 4 and concat(4,2,1) = 421 is prime;
aliquot parts of 1822 are 1, 2, 911 and concat(911,2,1) = 91121 is prime.
		

Links

• Paolo P. Lava, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A176553, A272141.

Programs

Maple

with(numtheory): P:= proc(q) local a,b,k,n;
for n from 1 to q do a:=sort([op(divisors(n))]); b:=0;
for k from nops(a)-1 by -1 to 1 do b:=b*10^(ilog10(a[k])+1)+a[k]; od;
if isprime(b) then print(n); fi; od; end: P(10^9);

Mathematica

Select[Range@ 362, PrimeQ@ FromDigits@ Flatten@ IntegerDigits@ Reverse@ Most@ Divisors@ # &] (* Michael De Vlieger, Apr 21 2016 *)