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%I #17 Jan 10 2019 23:38:18
%S 1,7,25,61,136,244,440,680,1022,1472,2198,2882,4065,5241,6681,8265,
%T 10866,13116,16726,19786,23566,27922,34270,38902,45502,52600,60430,
%U 68326,80941,89671,105047,116855,130913,146519,163214,177002,203013,224673,247605,268005,303306
%N Sum of distinct products i*j with 1 <= i, j <= n
%H Seiichi Manyama, <a href="/A321165/b321165.txt">Table of n, a(n) for n = 1..1000</a>
%F a(p) = a(p - 1) + p ^ 2 * (p + 1) / 2 for prime p. - _David A. Corneth_, Jan 10 2019
%e a(2) = 1 + 2 + 4 = 7.
%e a(3) = 1 + 2 + 3 + 4 + 6 + 9 = 25.
%o (PARI) a(n) = vecsum(setbinop((x, y)->x*y, vector(n, i, i); )); \\ _Michel Marcus_, Jan 10 2019
%Y Column 2 of A321163.
%Y Cf. A027424.
%K nonn
%O 1,2
%A _Seiichi Manyama_, Jan 10 2019
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