A081519 Sum of terms in row n of A081520.

1, 3, 10, 13, 51, 24, 148, 57, 109, 77, 606, 100, 1015, 161, 226, 241, 2313, 231, 3250, 318, 493, 425, 5820, 415, 1501, 605, 1054, 664, 11775, 593, 14416, 993, 1344, 1061, 1896, 946, 24643, 1337, 1931, 1302, 33621, 1204, 38830, 1737, 2124, 1985, 50808

Offset: 1

Author

Amarnath Murthy, Mar 27 2003

Keywords

• nonn

Comments

a(p) = p^2*(p-1)/2 + 1, p is prime.

a(p^k) = p^(k+1)*(p^k-1)/2 + 1 if p is prime and k >= 1. - Robert Israel, May 21 2015

Links

• Ivan Neretin, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A081518, A081520.

Programs

Maple

A:= proc(n) local L;
  L:= select(t->igcd(t,n)>1,[$1..n^2])[1 .. n-1];
  1+convert(L,`+`)
end proc:
seq(A(n),n=1..100); # Robert Israel, May 21 2015

Mathematica

Table[Plus @@ Join[{1}, Select[Range[n^2], GCD[n, #] > 1 &, n - 1]], {n, 1, 47}](* Ivan Neretin, May 21 2015 *)

Extensions

More terms from Ryan Propper, Nov 05 2005