login
A062676
Composite and every divisor (except 1) contains the digit 7.
18
497, 679, 749, 799, 1207, 1379, 1739, 1799, 1897, 2479, 2627, 2701, 2779, 3337, 3713, 3997, 4607, 4709, 4711, 4739, 4757, 4907, 5173, 5257, 5327, 5579, 5729, 5767, 5789, 6179, 6749, 6769, 6797, 6887, 6979, 7081, 7169, 7289, 7379, 7597, 7609, 7663
OFFSET
1,1
LINKS
EXAMPLE
799 has divisors 17, 47 and 799, all of which contain the digit 7.
MATHEMATICA
fQ[n_, dgt_] := Union[ MemberQ[#, dgt] & /@ IntegerDigits@ Rest@ Divisors@ n][[1]]; Select[ Range[2, 7670], !PrimeQ[#] && fQ[#, 7] &] (* Robert G. Wilson v, Jun 11 2014 *)
PROG
(Magma) [k:k in [2..8000]| not IsPrime(k) and forall{d:d in Set(Divisors(k)) diff {1}| 7 in Intseq(d)}]; // Marius A. Burtea, Nov 07 2019
KEYWORD
base,easy,nonn
AUTHOR
Erich Friedman, Jul 04 2001
EXTENSIONS
Offset corrected by Amiram Eldar, Nov 07 2019
STATUS
approved