A199595 Numbers n such that 3n+6, 3n+7 and 3n+8 are all composite.
1, 4, 9, 11, 14, 18, 21, 23, 24, 31, 32, 33, 34, 37, 40, 41, 44, 46, 49, 51, 54, 55, 60, 61, 62, 64, 65, 66, 71, 74, 75, 77, 79, 81, 84, 88, 89, 91, 92, 93, 94, 99, 100, 101, 102, 104, 106, 107, 111, 113, 114, 116, 118, 121, 123, 124, 127, 128, 130, 131, 134, 135, 138, 141, 143, 144, 149, 150, 151, 153, 154, 157, 158, 161, 163, 164, 165, 168, 169, 170
Offset: 1
References
- Ernest V. Miliauskas, letter to N. J. A. Sloane, Dec 21 1985.
Programs
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PARI
is(n)=!isprime(bitor(3*n+7,1)) \\ Charles R Greathouse IV, Jul 03 2013
Formula
a(n) = A199593(n)-8.