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A061352
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First row of array shown below.
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2
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1, 2, 6, 7, 5, 6, 8, 9, 5, 6, 6, 7, 1, 2, 0, 1, 3, 4, 0, 1, 1, 2, 6, 7, 5, 6, 8, 9, 5, 6, 6, 7, 1, 2, 0, 1, 3, 4, 0, 1, 1, 2, 6, 7, 5, 6, 8, 9, 5, 6, 6, 7, 1, 2, 0, 1, 3, 4, 0, 1, 1, 2, 6, 7, 5, 6, 8, 9, 5, 6, 6, 7, 1, 2, 0, 1, 3, 4, 0, 1, 1, 2, 6, 7, 5, 6, 8, 9, 5, 6, 6, 7, 1, 2, 0, 1, 3, 4, 0, 1, 1, 2, 6, 7, 5
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Least significant digit of the n-th triangular number if n is odd.
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FORMULA
| a(1)=1; if n odd, a(n+1)=(a(n)+1) mod 10; if n even, a(n+1)=(a(n)+2n) mod 10.
a(2n-1) = n*(2n-1)- 10*Floor[n*(2n-1)/10], a(2n) = n(2n+1)- 10*Floor[n*(2n+1)/10] + 1.
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EXAMPLE
| 1 2 6 7 5 6 8 9 5 ...
3 5 8 4 7 7 0 4 ...
4 9 3 8 6 1 3 ...
0 2 9 5 2 2 ...
1 0 4 3 1 ...
1 3 4 0 ...
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CROSSREFS
| Cf. A061353.
Sequence in context: A065488 A016591 A021793 * A173991 A039926 A035569
Adjacent sequences: A061349 A061350 A061351 * A061353 A061354 A061355
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KEYWORD
| nonn,easy
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 28 2001
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EXTENSIONS
| More terms and formula from Larry Reeves (larryr(AT)acm.org), May 15 2001
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