A127853 Numbers n such that A118680(n) = 1.

10, 17, 26, 36, 37, 45, 50, 59, 61, 65, 67, 78, 82, 90, 91, 94, 101, 102, 105, 108, 110, 122, 136, 138, 145, 147, 149, 153, 155, 165, 170, 173, 181, 183, 188, 189, 193, 197, 210, 213, 220, 224, 226, 231, 232, 239, 249, 250, 257, 262, 263, 266, 268, 276, 279

Offset: 1

Author

Alexander Adamchuk, Feb 03 2007

Keywords

• nonn

Comments

Also a(n) are the numbers n such that 1 + Sum[ k, {k,1,n} ] = 1 + n(n+1)/2 divides Product[ k, {k,1,n} ] = n!. A118680[ a(n) ] = 1, where A118680(n) = {2, 2, 7, 11, 2, 11, 29, 37, 23, 1, 67, 79, 23, 53, 11, 137, 1, ...} = Absolute value of numerator of determinant of n X n matrix with M(i,j) = (i+1)/i if i=j otherwise 1. A118680(n) = Numerator[ (1 + n(n+1)/2) / n! ].

Crossrefs

Cf. A118680, A118679, A127852.

Programs

Mathematica

Select[Range[1000],Numerator[(1 + #(#+1)/2)/#! ]==1&]