1,1

Divide the sequence of natural numbers: s0=1,2,3,4,5,6,7,8,9,10,11,12,13,14,... into sections s(n) of length 2*s1-1, where s1=initial digits of s(n): s={1,2},{3,4,5,6},{7,8,9,10,11,12,13,14},... then A1(n)=sum of terms of s(n):3,18,84,... A1(n)=3*2^(n-1)(2^n-1)=3*A006516(n)

Cf. A006516.

Sequence in context: A078904 A099012 A122069 this_sequence A119424 A037295 A124811

Adjacent sequences: A103894 A103895 A103896 this_sequence A103898 A103899 A103900

nonn

Zak Seidov (zakseidov(AT)yahoo.com), Mar 30 2005