|
| |
|
|
A257224
|
|
Numbers that have at least one divisor containing the digit 7 in base 10.
|
|
7
|
|
|
|
7, 14, 17, 21, 27, 28, 34, 35, 37, 42, 47, 49, 51, 54, 56, 57, 63, 67, 68, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 81, 84, 85, 87, 91, 94, 97, 98, 102, 105, 107, 108, 111, 112, 114, 117, 119, 126, 127, 133, 134, 135, 136, 137, 140, 141, 142, 144, 146, 147, 148
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
Numbers k whose concatenation of divisors A037278(k), A176558(k), A243360(k) or A256824(k) contains a digit 7.
A011537 (numbers that contain a 7) is a subsequence. - Michel Marcus, May 25 2015
|
|
|
LINKS
|
Table of n, a(n) for n=1..60.
|
|
|
FORMULA
|
a(n) ~ n.
|
|
|
EXAMPLE
|
14 is in sequence because the list of divisors of 14: (1, 2, 7, 14) contains digit 7.
|
|
|
MATHEMATICA
|
Select[Range@108, Part[Plus @@ DigitCount@ Divisors@ #, 7] > 0 &]
|
|
|
PROG
|
(MAGMA) [n: n in [1..1000] | [7] subset Setseq(Set(Sort(&cat[Intseq(d): d in Divisors(n)])))]
(PARI) is(n)=fordiv(n, d, if(setsearch(Set(digits(d)), 7), return(1))); 0
|
|
|
CROSSREFS
|
Cf. A037278, A176558, A243360, A256824.
Cf. similar sequences with another digit: A209932 (0), A000027 (1), A257219 (2), A257220 (3), A257221 (4), A257222 (5), A257223 (6), A257225 (8), A257226 (9).
Sequence in context: A198390 A118905 A254064 * A092433 A056203 A178732
Adjacent sequences: A257221 A257222 A257223 * A257225 A257226 A257227
|
|
|
KEYWORD
|
nonn,base
|
|
|
AUTHOR
|
Jaroslav Krizek, May 05 2015
|
|
|
EXTENSIONS
|
Mathematica and PARI programs with assistance from Michael De Vlieger and Charles R Greathouse IV, respectively.
|
|
|
STATUS
|
approved
|
| |
|
|
