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a(n) is the sum of terms in the n-th row of triangle A115758.
3

%I #18 Sep 29 2017 21:29:29

%S 0,1,4,7,14,19,28,34,45,53,72,80,96,105,119,139,168,179,213,234,248,

%T 269,312,327,363,391,430,452,493,530,570,593,645,677,732,756,801,844,

%U 885,922,981,1019,1100,1137,1188,1224,1283,1344,1397,1463,1524,1567,1668

%N a(n) is the sum of terms in the n-th row of triangle A115758.

%H Michael De Vlieger, <a href="/A115759/b115759.txt">Table of n, a(n) for n = 1..1000</a> (first 568 terms from Diana L. Mecum)

%t Fold[{Append[#1, #3], Append[#2, Total@ #3]} & @@ {First@ #1, Last@ #1, Map[Function[m, Count[Last@ #1, k_ /; CoprimeQ[m, k]]], Range@ #2]} &, {{{0}}, {0}}, Range[2, 53]] // Last (* _Michael De Vlieger_, Sep 29 2017 *)

%Y Cf. A115757, A115758.

%K nonn

%O 1,3

%A _Leroy Quet_, Jan 30 2006

%E a(7) and beyond from _Diana L. Mecum_, Aug 11 2008