3-rough numbers

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Least prime factor   ≥   3. The odd numbers:

a (n) = 2 n + 1

.

Sequences

A005408 3-rough numbers: positive integers that have no prime factors less than 3.

{1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, ...}

See also

• First row in an illustration for A002110, A005867, A038110, A060753.
• A016945 is the proper subset numbers with smallest prime factor 3.
• p-rough numbers

• 2-rough numbers
• 5-rough numbers
• 7-rough numbers
• 11-rough numbers
• 13-rough numbers
• 17-rough numbers
• 19-rough numbers
• 23-rough numbers