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A206347
Numbers n such that 10*n+1, 20*n+1, and 30*n+1 are all primes.
2
21, 27, 33, 60, 117, 153, 222, 228, 306, 426, 480, 495, 558, 585, 615, 636, 669, 684, 762, 768, 819, 852, 894, 909, 1083, 1125, 1131, 1224, 1239, 1341, 1455, 1512, 1539, 1776, 1812, 1845, 2301, 2484, 2517, 2541, 2604, 2706, 2769, 3093, 3177
OFFSET
1,1
COMMENTS
(10*n+1)*(20*n+1)*(30*n+1) is a Carmichael number for all n in this sequence. Why is (6m+1)*(12m+1)*(18m +1) used to generate Carmichael numbers and never the formula (10m+1)*(20m+1)*(30m+1)?
LINKS
MATHEMATICA
Select[Range[20000], PrimeQ[10 #+1] && PrimeQ[20 #+1] && PrimeQ[30 #+1]&]
CROSSREFS
Sequence in context: A365081 A352096 A103246 * A362008 A247316 A072392
KEYWORD
nonn
AUTHOR
STATUS
approved