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A206287 Numbers with all divisors starting with digit 1. 3
1, 11, 13, 17, 19, 101, 103, 107, 109, 113, 121, 127, 131, 137, 139, 143, 149, 151, 157, 163, 167, 169, 173, 179, 181, 187, 191, 193, 197, 199, 1009, 1013, 1019, 1021, 1031, 1033, 1039, 1049, 1051, 1061, 1063, 1069, 1087, 1091, 1093, 1097, 1103, 1109, 1111 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Equivalently, integers m with all divisors starting with the same first digit of m; in fact, as 1 divides all the integers, this digit is necessarily 1; also, for these terms m: A357299(m) = A000005(m). - Bernard Schott, Sep 25 2022
LINKS
EXAMPLE
All divisors of 187 (1, 11, 17, 187) start with digit 1.
MATHEMATICA
fQ[n_] := Module[{d = Divisors[n]}, Union[IntegerDigits[#][[1]] & /@ d] == {1}]; Select[Range[1111], fQ] (* T. D. Noe, Feb 13 2012 *)
CROSSREFS
Disjoint union of A045707 and A206288.
Cf. A004615 (with last digit)
Sequence in context: A262731 A087201 A068492 * A306661 A045707 A032591
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Feb 12 2012
STATUS
approved

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Last modified March 28 07:48 EDT 2024. Contains 371235 sequences. (Running on oeis4.)