A331758 A331757(n)/2.

4, 14, 40, 89, 186, 327, 562, 891, 1362, 1957, 2790, 3813, 5176, 6795, 8770, 11105, 14020, 17335, 21380, 25981, 31306, 37247, 44254, 52021, 60956, 70767, 81832, 93971, 107818, 122745, 139630, 158011, 178228, 199949, 223806, 249349, 277676, 307887

Offset

1,1

Links

Table of n, a(n) for n=1..38.

Mathematica

Table[(n^2 + 4n + 1 + Sum[Sum[(2 * Boole[GCD[i, j] == 1] - Boole[GCD[i, j] == 2]) * (n + 1 - i) * (n + 1 - j), {j, 1, n}], {i, 1, n}]) / 2, {n, 1, 38}] (* Joshua Oliver, Feb 05 2020 *)

Crossrefs

Cf. A331757.

Sequence in context: A144141 A187594 A326482 * A291675 A066375 A093160

Adjacent sequences: A331755 A331756 A331757 * A331759 A331760 A331761

Keyword

nonn

Author

N. J. A. Sloane, Feb 04 2020

Status

approved