A054425 A054424 expanded to normal triangular array, with zeros at those (x,y) where x and y are not relatively prime.

1, 2, 3, 4, 0, 7, 8, 5, 6, 15, 16, 0, 0, 0, 31, 32, 9, 11, 12, 14, 63, 64, 0, 10, 0, 13, 0, 127, 128, 17, 0, 23, 24, 0, 30, 255, 256, 0, 19, 0, 0, 0, 28, 0, 511, 512, 33, 18, 20, 47, 48, 27, 29, 62, 1023, 1024, 0, 0, 0, 22, 0, 25, 0, 0, 0, 2047, 2048, 65, 35, 39, 21, 95, 96, 26, 56

Offset: 1

Author

Antti Karttunen

Keywords

• nonn
• tabl
• nice

Crossrefs

Cf. A054424, A054431.

Programs

Maple

position_in_whole_SB_tree_or_zero := (n,m) -> `if`((1 = gcd(n,m)),(frac2position_in_whole_SB_tree(n/m)),(0));
A054424_as_array := n -> position_in_whole_SB_tree_or_zero( ((n-((trinv(n)*(trinv(n)-1))/2))+1), ((((trinv(n)-1)*(((1/2)*trinv(n))+1))-n)+1) );
trinv := n -> floor((1+sqrt(1+8*n))/2); # Gives integral inverses to the triangular numbers