1,1

a(n) = semiprime(n) + n(n+1)/2.

Cf. A000217, A111440, A112662.

Sequence in context: A130683 A091040 A029985 this_sequence A145823 A121142 A087296

Adjacent sequences: A114020 A114021 A114022 this_sequence A114024 A114025 A114026

nonn

Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Feb 01 2006