A114104 a(n) = A114103(n)/n.

1, 1, 2, 3, 3, 1, 4, 1, 4, 2, 5, 5, 5, 5, 1, 3, 6, 1, 6, 3, 2, 7, 7, 7, 7, 7, 7, 1, 8, 4, 8, 1, 8, 4, 8, 2, 9, 9, 3, 9, 9, 3, 9, 9, 1, 5, 10, 5, 10, 1, 10, 5, 10, 5, 2, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 1, 12, 3, 4, 6, 12, 1, 12, 6, 4, 3, 12, 2, 13, 13

Offset

1,3

Comments

Iff k appears k-1 times successively then k is prime.

Links

Table of n, a(n) for n=1..80.

Maple

A000217 := proc(n) n*(n+1)/2 ; end: A003056 := proc(n) floor((sqrt(1+8*n)-1)/2) ; end: A114103 := proc(n, k) lcm(n, A000217(n-1)+k) ; end: A114104 := proc(n) local row, col ; row := A003056(n-1)+1 ; col := n-A000217(row-1) ; A114103(row, col)/n ; end: for n from 1 to 80 do printf("%d, ", A114104(n)) ; od ; # R. J. Mathar, May 10 2007

Mathematica

rows = 13;
nmax = rows (rows + 1)/2;
A114103 = Flatten[Table[LCM[n, n (n-1)/2 + k], {n, rows}, {k, n}]];
a[n_] := A114103[[n]]/n;
Table[a[n], {n, 1, nmax}] (* Jean-François Alcover, May 23 2024, after Ivan Neretin in A114103 *)

Crossrefs

Cf. A114103, A114105.

Sequence in context: A172528 A087074 A136453 * A076780 A324733 A274604

Adjacent sequences: A114101 A114102 A114103 * A114105 A114106 A114107

Keyword

nonn

Author

Amarnath Murthy, Nov 21 2005

Extensions

Corrected and extended by R. J. Mathar, May 10 2007

Status

approved