A272141 Numbers such that the concatenation of their aliquot parts, in ascending order, are prime numbers.
9, 14, 21, 26, 27, 34, 35, 46, 49, 55, 57, 58, 62, 74, 98, 115, 118, 143, 155, 158, 161, 166, 169, 178, 183, 187, 194, 201, 202, 209, 214, 215, 218, 219, 221, 226, 245, 265, 279, 287, 295, 298, 309, 314, 323, 326, 327, 329, 335, 341, 355, 371, 374, 377, 381
Offset: 1
Examples
Aliquot parts of 9 are 1, 3 and concat(1,3) = 13 is prime; aliquot parts of 3127 are 1, 53, 59 and concat(1,53,59) = 15359 is prime.
Links
- Paolo P. Lava, Table of n, a(n) for n = 1..10000
Programs
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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 1 to nops(a)-1 do b:=b*10^(ilog10(a[k])+1)+a[k]; od; if isprime(b) then print(n); fi; od; end: P(10^9);
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Mathematica
Select[Range@ 384, PrimeQ@ FromDigits@ Flatten@ IntegerDigits@ Most@ Divisors@ # &] (* Michael De Vlieger, Apr 21 2016 *)