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A114104
a(n) = A114103(n)/n.
3
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.
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
Sequence in context: A172528 A087074 A136453 * A076780 A324733 A274604
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Nov 21 2005
EXTENSIONS
Corrected and extended by R. J. Mathar, May 10 2007
STATUS
approved