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A134928
Triple composites.
6
4, 6, 8, 10, 12, 14, 16, 18, 20, 28, 30, 32, 40, 42, 44, 58, 60, 62, 70, 72, 74, 100, 102, 104, 106, 108, 110, 136, 138, 140, 148, 150, 152, 178, 180, 182, 190, 192, 194, 196, 198, 200, 226, 228, 230, 238, 240, 242, 268, 270, 272, 280, 282, 284
OFFSET
1,1
COMMENTS
Numbers that are composites and nearest-neighbors of twin primes.
EXAMPLE
28, 30 and 32 are triple composites because 29 and 31 are twin primes and 28, 30 and 32 are composites and nearest-neighbors of 29 and 31.
MATHEMATICA
#[[1]]+{-1, 1, 3}&/@Select[Partition[Prime[Range[3, 100]], 2, 1], #[[2]]-#[[1]]==2&]//Flatten (* Harvey P. Dale, Jun 09 2023 *)
Flatten[{#[[1]], #[[1]]+2, #[[2]]}&/@SequencePosition[Table[Which[CompositeQ[ n], 1, PrimeQ[ n], 2, True, 0], {n, 300}], {1, 2, 1, 2, 1}]] (* Harvey P. Dale, Sep 07 2023 *)
CROSSREFS
Cf. Twin primes = A001097, Composite numbers = A002808.
Sequence in context: A210939 A175246 A353537 * A279040 A141109 A333197
KEYWORD
easy,nonn
AUTHOR
Omar E. Pol, Nov 16 2007
STATUS
approved