A103408 Numbers n such that n2101 is prime.
1, 4, 7, 10, 18, 24, 25, 28, 31, 34, 39, 42, 48, 51, 63, 70, 73, 76, 79, 81, 85, 93, 94, 100, 126, 139, 148, 150, 156, 157, 160, 163, 168, 174, 177, 184, 186, 199, 202, 207, 219, 232, 234, 235, 237, 265, 268, 277, 300, 301, 307, 309, 315, 316, 321, 322, 328, 343, 354, 358, 364, 366
Offset: 1
Examples
If n=1, then n2101 = 12101 (prime). If n=31, then n2101 = 312101 (prime). If n=63, then n2101 = 632101 (prime).
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Programs
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Magma
[ n: n in [1..700] | IsPrime(Seqint([1, 0, 1, 2] cat Intseq(n))) ]; // Vincenzo Librandi, Feb 03 2011
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Mathematica
Select[Range[400],PrimeQ[10000#+2101]&] (* Harvey P. Dale, Jul 20 2015 *)
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PARI
is(n)=isprime(10000*n+2101) \\ Charles R Greathouse IV, Jun 06 2017