Number of distinct products ij with 1 <= i < j <= n. (Number of terms appearing more than once in a 1-to-n multiplication table.)
A027428
Number of distinct products ij with 1 <= i < j <= n. (Number of terms appearing more than once in a 1-to-n multiplication table.)
Terms
- a(0) =0a(1) =1a(2) =3a(3) =6a(4) =10a(5) =13a(6) =19a(7) =24a(8) =31a(9) =36a(10) =46a(11) =51a(12) =63a(13) =70a(14) =78a(15) =87a(16) =103a(17) =111a(18) =129a(19) =139a(20) =150a(21) =161a(22) =183a(23) =192a(24) =210a(25) =223a(26) =239a(27) =252a(28) =280a(29) =291
External references
- oeis: A027428