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A257221
Numbers that have at least one divisor containing the digit 4 in base 10.
8
4, 8, 12, 14, 16, 20, 24, 28, 32, 34, 36, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 52, 54, 56, 60, 64, 68, 70, 72, 74, 76, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 108, 112, 114, 116, 120, 123, 124, 126, 128, 129, 132, 134, 135, 136, 138, 140, 141
OFFSET
1,1
COMMENTS
Numbers k whose concatenation of divisors A037278(k), A176558(k), A243360(k) or A256824(k) contains a digit 4.
Sequences of numbers k whose concatenation of divisors contains a digit j in base 10 for 0 <= j <= 9: A209932 for j = 0, A000027 for j = 1, A257219 for j = 2, A257220 for j = 3, A257221 for j = 4, A257222 for j = 5, A257223 for j = 6, A257224 for j = 7, A257225 for j = 8, A257226 for j = 9.
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
FORMULA
a(n) ~ n. - Charles R Greathouse IV, Apr 30 2015
EXAMPLE
16 is in sequence because the list of divisors of 16: (1, 2, 4, 8, 16) contains digit 4.
MATHEMATICA
Select[Range@ 141, Part[Plus @@ DigitCount@ Divisors@ #, 4] > 0 &] (* Michael De Vlieger, Apr 20 2015 *)
Select[Range[200], Count[Flatten[IntegerDigits/@Divisors[#]], 4]>0&] (* Harvey P. Dale, May 05 2022 *)
PROG
(Magma) [n: n in [1..1000] | [4] subset Setseq(Set(Sort(&cat[Intseq(d): d in Divisors(n)])))]
(PARI) is(n)=fordiv(n, d, if(setsearch(Set(digits(d)), 4), return(1))); 0 \\ Charles R Greathouse IV, Apr 30 2015
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Apr 20 2015
STATUS
approved