A336307 Numbers that are neither Colombian nor Brazilian.
2, 4, 6, 11, 17, 19, 23, 25, 29, 37, 41, 47, 49, 59, 61, 67, 71, 79, 83, 89, 101, 103, 107, 109, 113, 131, 137, 139, 149, 151, 163, 167, 169, 173, 179, 181, 191, 193, 197, 199, 223, 227, 229, 239, 251, 257, 263, 269, 271, 281, 283, 289, 293, 311, 313, 317, 331
Offset: 1
Examples
For b = 17, there is no repdigit in some base b < 16 equal to 17, hence 17 is not Brazilian and 17 = 13 + (sum of digits of 13) hence 17 is not Colombian, so 17 is a term.
Links
- Giovanni Resta, Self or Colombian number, Numbers Aplenty.
- Wikipédia, Nombre brésilien.
- Wikipedia, Partition of a set.
- Index to sequences related to Brazilian Numbers.
- Index to sequences related to Colombian Numbers.
Crossrefs
Programs
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Mathematica
brazQ[n_] := Module[{b = 2, found = False}, While[b < n - 1 && Length[ Union[ IntegerDigits[n, b]]] > 1, b++]; b < n - 1]; n = 300; Select[Union @ Table[Plus @@ IntegerDigits[k] + k, {k, 1, n}], # <= n && !brazQ[#] &] (* Amiram Eldar, Jul 17 2020 *)
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