A069268 Greatest common divisor of n! and n*(n+1)/2.

1, 1, 6, 2, 15, 3, 28, 36, 45, 5, 66, 6, 91, 105, 120, 8, 153, 9, 190, 210, 231, 11, 276, 300, 325, 351, 378, 14, 435, 15, 496, 528, 561, 595, 630, 18, 703, 741, 780, 20, 861, 21, 946, 990, 1035, 23, 1128, 1176, 1225, 1275, 1326

Offset

1,3

Links

Paolo P. Lava, Table of n, a(n) for n = 1..10000

Formula

a(n) = if n>1 and n+1 is prime then n/2 else n*(n+1)/2.

Mathematica

Table[GCD[n!, (n(n+1))/2], {n, 60}] (* Harvey P. Dale, Oct 14 2013 *)

Crossrefs

Cf. A000142, A000217, A000040.

Cf. A090585, A090586.

Sequence in context: A080977 A095951 A116420 * A348060 A082155 A128225

Adjacent sequences: A069265 A069266 A069267 * A069269 A069270 A069271

Keyword

nonn

Author

Reinhard Zumkeller, Apr 14 2002

Status

approved