A290016 Brazilian numbers which have exactly three Brazilian representations.

24, 36, 42, 54, 66, 70, 78, 88, 100, 102, 104, 105, 124, 128, 130, 135, 136, 138, 152, 154, 165, 171, 172, 174, 182, 184, 186, 189, 190, 195, 196, 225, 230, 231, 232, 238, 242, 246, 248, 250, 256, 258, 272, 282, 286, 290, 292, 296, 297, 310, 318, 322, 328, 333, 344, 345

Offset

1,1

Comments

These numbers could be called 3-Brazilian numbers.

All these numbers are composite with six to ten different divisors.

The smallest number of this sequence is 24 with 24 = 44_5 = 33_7 = 22_11. The number 24 is highly Brazilian in A329383.

Links

Table of n, a(n) for n=1..56.

Example

36 = 4 * 9 = 44_8 = 3 * 12 = 33_11 = 2 * 18 = 22_19.
42 = 2 * 21 = 22_20 = 222_4 = 3 * 14 = 33_13.
124 = 4 * 31 = 44_30 = 444_5 = 2 * 62 = 22_61.
272 = 8 * 34 = 88_33 = 4 * 68 = 44_67 = 2 * 136 = 22_135.

Mathematica

Flatten@ Position[#, 3] &@ Table[Count[Range[2, n - 2], _?(And[Length@ # != 1, Length@ Union@ # == 1] &@ IntegerDigits[n, #] &)], {n, 350}] (* Michael De Vlieger, Jul 30 2017 *)

Crossrefs

Cf. A125134, A220570, A220571, A257521, A288783, A290015, A290017, A290018, A329383.

Sequence in context: A307342 A067341 A307682 * A330880 A195008 A054775

Adjacent sequences: A290013 A290014 A290015 * A290017 A290018 A290019

Keyword

nonn

Author

Bernard Schott, Jul 27 2017

Status

approved