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

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..1000

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 *)

Crossrefs

Cf. A002858, A068820, A307328, A307329.

Sequence in context: A251453 A087002 A256743 * A046394 A163304 A252237

Adjacent sequences: A307327 A307328 A307329 * A307331 A307332 A307333

Keyword

nonn,changed

Author

Amiram Eldar, Apr 02 2019

Status

approved