A025051 Numbers of the form j*k + k*i + i*j, where i,j,k >= 1.

3, 5, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 19, 20, 21, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, 72, 73, 74, 75, 76, 77, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88

Offset

1,1

Links

Table of n, a(n) for n=1..76.

J. Borwein and K.-K. S. Choi, On the representations of xy+yz+zx, Experimental Mathematics, 9 (2000), 153-158.

Index entries for linear recurrences with constant coefficients, signature (2,-1).

Formula

On the GRH, a(n) = n + 18 for n > 444. If there is some N > 444 with a(N) not equal to n + 19, then for n >= N, a(n) = n + 19 (and GRH is false). See Borwein & Choi. - Charles R Greathouse IV, Dec 19 2022

n is in the sequence if and only if A066955(n) > 0. - Charles R Greathouse IV, Jun 25 2024

Mathematica

Take[Union[Total[Times@@@Subsets[#, {2}]]&/@Tuples[Range[25], {3}]], 80] (* Harvey P. Dale, Aug 11 2011 *)

Crossrefs

Uniquification of sequence A025050.

Cf. A025052 (complement), A066955.

Sequence in context: A025050 A196115 A336867 * A020884 A183855 A024352

Adjacent sequences: A025048 A025049 A025050 * A025052 A025053 A025054

Keyword

nonn,nice,easy

Author

Clark Kimberling

Status

approved