A185348 Number of ordered quadruples of distinct pairwise coprime positive integers with largest element n; also first differences of A015623.

0, 0, 0, 0, 2, 0, 8, 4, 10, 2, 42, 4, 79, 16, 25, 36, 183, 20, 277, 50, 100, 70, 491, 56, 399, 139, 340, 146, 1016, 56, 1285, 398, 493, 342, 706, 184, 2150, 501, 807, 363, 2968, 210, 3522, 775, 935, 904, 4620, 508, 3732, 842, 2011, 1255, 6684, 728, 3355, 1304, 2785, 1877, 9141, 546

Offset

1,5

Links

Alois P. Heinz, Table of n, a(n) for n = 1..1000

Example

a(4) = 0 because there is only one ordered quadruple of distinct positive integers with largest element 4, (1,2,3,4), but the elements are not pairwise coprime, 2 and 4 have a common factor >1.
a(8) = 4 because there are only four ordered quadruples of distinct pairwise coprime positive integers with largest element 8: (1,3,5,8), (1,3,7,8), (1,5,7,8), (3,5,7,8).

Crossrefs

Cf. A015623, A185953. Column 4 of triangle A186972.

Sequence in context: A252852 A351483 A154909 * A321599 A020780 A334071

Adjacent sequences: A185345 A185346 A185347 * A185349 A185350 A185351

Keyword

nonn

Author

Alois P. Heinz, Feb 15 2011

Status

approved