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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

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Last modified March 4 20:58 EST 2021. Contains 341811 sequences. (Running on oeis4.)