A185348 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

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

(list; graph; refs; listen; history; text; internal format)

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: A370692 A373564 A154909 * A321599 A020780 A377567

Adjacent sequences: A185345 A185346 A185347 * A185349 A185350 A185351

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Feb 15 2011

STATUS

approved