A321165 Sum of distinct products i*j with 1 <= i, j <= n

1, 7, 25, 61, 136, 244, 440, 680, 1022, 1472, 2198, 2882, 4065, 5241, 6681, 8265, 10866, 13116, 16726, 19786, 23566, 27922, 34270, 38902, 45502, 52600, 60430, 68326, 80941, 89671, 105047, 116855, 130913, 146519, 163214, 177002, 203013, 224673, 247605, 268005, 303306

Offset

1,2

Links

Seiichi Manyama, Table of n, a(n) for n = 1..1000

Formula

a(p) = a(p - 1) + p ^ 2 * (p + 1) / 2 for prime p. - David A. Corneth, Jan 10 2019

Example

a(2) = 1 + 2 + 4 = 7.
a(3) = 1 + 2 + 3 + 4 + 6 + 9 = 25.

Prog

(PARI) a(n) = vecsum(setbinop((x, y)->x*y, vector(n, i, i); )); \\ Michel Marcus, Jan 10 2019

Crossrefs

Column 2 of A321163.

Cf. A027424.

Sequence in context: A061600 A098538 A033814 * A344560 A118395 A118396

Adjacent sequences: A321162 A321163 A321164 * A321166 A321167 A321168

Keyword

nonn

Author

Seiichi Manyama, Jan 10 2019

Status

approved