1,1

A109986 is primes ordered alphabetically by where they occur in A000052. A109987 is semiprimes ordered alphabetically by where they occur in A000052. A109989 is 4-almost primes ordered alphabetically by where they occur in A000052.

a(1) = 8 because eight is the first 3-almost prime in alphabetical order.

a(4) = 18 because eighteen is the first 2-digit 3-almost prime in alphabetical order.

Cf. A000052, A014612, A109986, A109987.

Sequence in context: A096283 A082194 A034714 this_sequence A066721 A079704 A133581

Adjacent sequences: A109985 A109986 A109987 this_sequence A109989 A109990 A109991

base,easy,nonn,word

Jonathan Vos Post (jvospost2(AT)yahoo.com), Jul 07 2005