1,2

a(n) = n*10^(n-1) + n(n-1)/2.

Cf. A081551, A081552.

Sequence in context: A079517 A021784 A019618 this_sequence A021524 A021268 A018069

Adjacent sequences: A081550 A081551 A081552 this_sequence A081554 A081555 A081556

base,easy,nonn

Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 01 2003