A362074 a(n) is the rank of the n X n symmetric matrix M(n) whose generic element M[i,j] = digsum(i*j).
1, 1, 1, 3, 5, 6, 7, 7, 7, 7, 7, 9, 11, 11, 13, 14, 15, 16, 18, 18, 18, 19, 19, 21, 23, 24, 25, 26, 27, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63
Offset: 1
Programs
-
Mathematica
M[i_, j_]:=Total[IntegerDigits[i*j]]; Table[MatrixRank[Table[M[i, j], {i, n}, {j, n}]], {n, 69}] -
PARI
a(n)=matrank(matrix(n,n,i,j,sumdigits(i*j))) \\ Andrew Howroyd, Apr 08 2023
Comments