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A245717
Triangle read by rows: T(n,k) = gcd(n,k^2), 1 <= k <= n.
4
1, 1, 2, 1, 1, 3, 1, 4, 1, 4, 1, 1, 1, 1, 5, 1, 2, 3, 2, 1, 6, 1, 1, 1, 1, 1, 1, 7, 1, 4, 1, 8, 1, 4, 1, 8, 1, 1, 9, 1, 1, 9, 1, 1, 9, 1, 2, 1, 2, 5, 2, 1, 2, 1, 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11, 1, 4, 3, 4, 1, 12, 1, 4, 3, 4, 1, 12, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 13
OFFSET
1,3
LINKS
EXAMPLE
First rows and their sums (A078430):
. 1: 1 1
. 2: 1, 2 3
. 3: 1, 1, 3 5
. 4: 1, 4, 1, 4 10
. 5: 1, 1, 1, 1, 5 9
. 6: 1, 2, 3, 2, 1, 6 15
. 7: 1, 1, 1, 1, 1, 1, 7 13
. 8: 1, 4, 1, 8, 1, 4, 1, 8 28
. 9: 1, 1, 9, 1, 1, 9, 1, 1, 9 33
. 10: 1, 2, 1, 2, 5, 2, 1, 2, 1, 10 27
. 11: 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11 21
. 12: 1, 4, 3, 4, 1, 12, 1, 4, 3, 4, 1, 12 50
MATHEMATICA
Table[GCD[n, k^2], {n, 15}, {k, n}]//Flatten (* Harvey P. Dale, Nov 05 2022 *)
PROG
(Haskell)
a245717 n k = a245717_tabl !! (n-1) !! (k-1)
a245717_row n = a245717_tabl !! (n-1)
a245717_tabl = zipWith (zipWith gcd) a002024_tabl a133819_tabl
(PARI) row(n) = vector(n, k, gcd(n, k^2)); \\ Michel Marcus, Jan 24 2022
CROSSREFS
Cf. A050873, A002024, A133819, A078430 (row sums).
Sequence in context: A089141 A336084 A375128 * A248008 A327981 A348447
KEYWORD
nonn,tabl
AUTHOR
Reinhard Zumkeller, Jul 30 2014
STATUS
approved