A008471 Exactly 3 out of 10m+1, 10m+3, 10m+7, 10m+9 are primes.

4, 7, 13, 22, 31, 43, 46, 61, 64, 85, 88, 103, 106, 109, 130, 142, 145, 160, 166, 169, 178, 199, 238, 268, 271, 316, 367, 376, 391, 400, 409, 415, 421, 451, 472, 478, 493, 523, 541, 544, 547, 550, 574

Offset: 1

Author

Olivier Gérard

Keywords

• nonn

Links

• V. Raman, Table of n, a(n) for n = 1..10000 (first 1000 terms from Harvey P. Dale)

Crossrefs

Cf. A007811, A032352, A216292, A216293.

Programs

Magma

[n: n in [1..600] | #PrimesInInterval(10*n+1, 10*n+9) eq 3]; // Bruno Berselli, Sep 04 2012

Mathematica

m3Q[m_]:=Module[{c=10m},Count[{c+1,c+3,c+7,c+9},?PrimeQ]==3]; Select[ Range[ 600],m3Q] (* _Harvey P. Dale, Dec 24 2011 *)
Select[Range[600],Total[Boole[PrimeQ[10 #+{1,3,7,9}]]]==3&] (* Harvey P. Dale, Jul 27 2025 *)