A134928 Triple composites.

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

Author

Omar E. Pol, Nov 16 2007

Keywords

• easy
• nonn

Comments

Numbers that are composites and nearest-neighbors of twin primes.

Examples

			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.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000
• Omar E. Pol, Determinacion geometrica de los numeros primos y compuesto.

Crossrefs

Cf. Twin primes = A001097, Composite numbers = A002808.

Programs

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 *)