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A205001
Least k such that n divides the k-th difference between distinct triangular numbers.
1
1, 1, 3, 6, 2, 8, 5, 28, 4, 11, 14, 8, 20, 7, 13, 120, 35, 12, 44, 11, 26, 18, 65, 34, 17, 25, 16, 49, 104, 24, 119, 496, 23, 42, 22, 58, 170, 52, 31, 41, 209, 30, 230, 29, 40, 75, 275, 134, 39, 62, 50, 38, 350, 37, 74, 49, 61, 117, 434, 48
OFFSET
1,3
COMMENTS
For a guide to related sequences, see A204892.
EXAMPLE
The triangular numbers: s(k)=k(k+1)/2.
Their differences, ordered as in A193974:
u(1)=s(2)-s(1)=2
u(2)=s(3)-s(1)=5
u(3)=s(3)-s(2)=3
u(4)=s(4)-s(1)=9
u(5)=s(4)-s(2)=7
u(6)=s(4)-s(3)=4.
a(1)=1 because 1 divides u(1)
a(2)=1 because 2 divides u(1)
a(3)=3 because 3 divides u(3)
a(4)=6 because 4 divides u(6)
a(5)=2 because 5 divides u(2)
a(6)=8 because 6 divides u(8)
MATHEMATICA
(See the program at A205002.)
CROSSREFS
Sequence in context: A244619 A330576 A099506 * A154204 A309609 A266971
KEYWORD
nonn
AUTHOR
Clark Kimberling, Jan 21 2012
STATUS
approved