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A061353 First column of array shown in A061352. 2
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, 6, 8, 9, 5, 6, 6, 7, 1, 2, 0, 1, 3, 4, 0, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Least significant digit of the n-th triangular number if n is even.
LINKS
FORMULA
a(1)=1; if n even, a(n+1)=(a(n)+1) mod 10; if n odd, a(n+1)=(a(n)+2n) mod 10.
a(2n-1) = n*(2n-1)- 10*Floor[n*(2n-1)/10] +1, a(2n) = n(2n+1)- 10*Floor[n*(2n+1)/10].
CROSSREFS
Sequence in context: A131099 A098800 A087666 * A016653 A096088 A107681
KEYWORD
nonn,easy
AUTHOR
Amarnath Murthy, Apr 28 2001
EXTENSIONS
More terms and formula from Larry Reeves (larryr(AT)acm.org), May 15 2001
STATUS
approved

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Last modified March 28 16:58 EDT 2024. Contains 371254 sequences. (Running on oeis4.)