A133764 Composite numbers such that any two terms, plus 1, yields a composite number:.

4, 9, 10, 15, 16, 22, 28, 34, 35, 39, 40, 46, 52, 58, 64, 70, 75, 76, 82, 88, 94, 100, 106, 112, 118, 119, 124, 125, 130, 136, 142, 148, 154, 160, 166, 172, 178, 184, 190, 196, 202, 208, 209, 214, 220, 226, 232, 238, 244, 249, 250, 256, 262, 268, 274, 279, 280

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

15 is a term of the sequence because 15 is composite and 15+4+1, 15+9+1 and 15+10+1, are all composite (20,25 and 36, respectively).

Maple

R:= {4}:
for r from 5 to 1000 do
  if not isprime(r) and not ormap(isprime, R +~ (r+1)) then
    R:= R union {r}
  fi
od:
sort(convert(R, list)); # Robert Israel, May 11 2025

Crossrefs

Cf. A002808 (composite numbers).

Sequence in context: A358762 A157908 A064973 * A163643 A139558 A219556

Adjacent sequences: A133761 A133762 A133763 * A133765 A133766 A133767

Keyword

easy,nonn

Author

Randy L. Ekl, Jan 01 2008

Status

approved