1,3

M * V where M = A054521 is an infinite lower triangular matrix and V = A000217: (1, 3, 6, 10,...).

a(6) = 16 since the relative primes of 6 are 1 and 5 and (1 + 15) = 16.

Cf. A000217.

Sequence in context: A140167 A006130 A133264 this_sequence A045548 A090879 A084404

Adjacent sequences: A127412 A127413 A127414 this_sequence A127416 A127417 A127418

nonn

Gary W. Adamson (qntmpkt(AT)yahoo.com), Jan 13 2007