A307330 Indices of Ulam prime triples, where u(k), u(k+1) and u(k+2) are all primes, and u(k) = A002858(k) are the Ulam numbers.
858, 1547, 2515, 3059, 9503, 9781, 11899, 11900, 13622, 15413, 18928, 22829, 25462, 32020, 33021, 33963, 36598, 37811, 37854, 40046, 44447, 49104, 55249, 56526, 60847, 61741, 80658, 84414, 86235, 87971, 92832, 96674, 97185, 100004, 102684, 108025, 108273
Offset: 1
Keywords
Links
- Amiram Eldar, Table of n, a(n) for n = 1..1000
Programs
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Mathematica
ulams = {1, 2}; Do[AppendTo[ulams, n = Last[ulams]; While[n++; Length[ DeleteCases[Intersection[ulams, n - ulams], n/2, 1, 1]] != 2]; n], {1000}]; p = PrimeQ[ulams]; len = Length[p]; s={}; Do[If[p[[n]]&&p[[n+1]]&&p[[n+2]], AppendTo[s,n]], {n,1,len-2}]; s (* after Jean-François Alcover at A002858 *)