1,2

A024451(n) gives the sum of the n-th row.

When parsed in blocks of ascending length, as shown in the example, there is the following interpretation: The integers Z regarded as a module over themselves contains unshortenable generating sets of different lengths, in fact, infinitely many of each desired length. Each of the blocks is the minimal example of an unshortenable generating set of the respective length. For example, {6,10,15} generates Z as 1=6+10-15. However, removing one of the numbers leaves two numbers that are not relatively prime, precluding generation of Z. An analogous argument succeeds for all other blocks alike. Each block contains numbers such that there is no prime factor common to all. Taking differences sufficiently often one ends up with two coprime numbers whence the generating property follows from Bezout's theorem. Removing just one number from the set, relative primality is lost. The minimality of the numbers used in each block is evident from the construction. - Peter C. Heinig (algorithms(AT)gmx.de), Oct 04 2006

1; 2,3; 6,10,15; 30,42,70,105; 210...

Cf. A024451.

Sequence in context: A074134 A056178 A018141 this_sequence A055789 A048681 A051891

Adjacent sequences: A077008 A077009 A077010 this_sequence A077012 A077013 A077014

nonn,tabl

Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Oct 26 2002

More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Jan 26 2003