A115394 List of triples of semiprimes: each three numbers are consecutive semiprimes.

33, 34, 35, 85, 86, 87, 93, 94, 95, 121, 122, 123, 141, 142, 143, 201, 202, 203, 213, 214, 215, 217, 218, 219, 301, 302, 303, 393, 394, 395, 445, 446, 447, 633, 634, 635, 697, 698, 699, 841, 842, 843, 921, 922, 923, 1041, 1042, 1043, 1137, 1138, 1139, 1261

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(3n-2) = A056809(n), a(3n-1) = A086005(n), a(3n) = A086005(n) + 1 = 2*A086006(n) + 1, n=1,2,...

Mathematica

Flatten[Select[Partition[Union[Times@@@Tuples[Prime[Range[150]], {2}]], 3, 1], #[[3]]-#[[2]]==#[[2]]-#[[1]]==1&]]  (* Harvey P. Dale, Jan 22 2011 *)
{#[[1]], #[[1]]+1, #[[2]]}&/@SequencePosition[Table[If[PrimeOmega[n]==2, 1, 0], {n, 1500}], {1, 1, 1}]//Flatten (* Harvey P. Dale, Nov 07 2025 *)

Crossrefs

Cf. A056809, A086005, A086006.

Sequence in context: A291436 A165854 A112817 * A344143 A335072 A260678

Adjacent sequences: A115391 A115392 A115393 * A115395 A115396 A115397

Keyword

nonn

Author

Zak Seidov, Mar 08 2006

Status

approved