A144020 Numbers of the form 1+i^2+j^2+k^2 with 1 <= i <= j <= k.

4, 7, 10, 12, 13, 15, 18, 19, 20, 22, 23, 25, 27, 28, 30, 31, 34, 35, 36, 37, 39, 42, 43, 44, 45, 46, 47, 49, 50, 51, 52, 54, 55, 57, 58, 60, 62, 63, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79, 82, 83, 84, 85, 87, 89, 90, 91, 92, 94, 95, 97, 98, 99, 100, 102, 103, 105, 106

Offset: 1

Author

N. J. A. Sloane, Dec 02 2008, Dec 21 2008

Keywords

• nonn

Comments

No number == -1 mod 8 is a sum of three squares, so multiples of 8 are missing from this sequence.

It appears that numbers == 1 mod 16 are also missing from the sequence.

Formula

a(n) = 1+A000408(n). [From R. J. Mathar, Dec 03 2008]