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A201822
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Numbers n such that 90*n + 77 is prime.
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13
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1, 2, 3, 6, 8, 9, 10, 15, 17, 18, 19, 20, 24, 26, 29, 30, 32, 34, 37, 40, 41, 43, 45, 46, 48, 54, 58, 59, 60, 62, 65, 68, 69, 74, 75, 76, 79, 82, 83, 85, 86, 87, 89, 93, 94, 95, 97, 102, 104, 109, 111, 113, 114, 115, 117, 122, 128, 130, 131, 135, 138, 144
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listen;
history;
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internal format)
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OFFSET
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1,2
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COMMENTS
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Looking at the format 90n+77 modulo 9 and modulo 10 we see that all entries of A142329 have digital root 5 and last digit 7. (Reverting the process is an application of the Chinese remainder theorem.)
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 1..10000
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FORMULA
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a(n)= (A142329(n)-77)/90.
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MATHEMATICA
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Select[Range[0, 400], PrimeQ[90 #+77]&] (* Vincenzo Librandi, Dec 11 2011 *)
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PROG
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(MAGMA) [n: n in [0..200] | IsPrime(90*n+77)]; // Vincenzo Librandi, Dec 11 2011
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CROSSREFS
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Cf. A181732, A198382, A195993, A196000, A196007, A201739, A201734, A201804, A201816, A201817, A201818, A201820.
Sequence in context: A175904 A084090 A047286 * A093510 A202341 A013948
Adjacent sequences: A201819 A201820 A201821 * A201823 A201824 A201825
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KEYWORD
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nonn,easy
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AUTHOR
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J. W. Helkenberg, Dec 05 2011
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STATUS
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approved
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