A061353 - OEIS

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A061353

First column of array shown in A061352.

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; internal format)

	OFFSET	`1,2`
	COMMENTS	`Least significant digit of the n-th triangular number if n is even.`
	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)- 10Floor[n(2n-1)/10] +1, a(2n) = n(2n+1)- 10Floor[n*(2n+1)/10].`
	CROSSREFS	`Sequence in context: A131099 A098800 A087666 * A016653 A096088 A107681` `Adjacent sequences: A061350 A061351 A061352 * A061354 A061355 A061356`
	KEYWORD	`nonn,easy`
	AUTHOR	`Amarnath_murthy (amarnath_murthy(AT)yahoo.com), Apr 28 2001`
	EXTENSIONS	`More terms and formula from Larry Reeves (larryr(AT)acm.org), May 15 2001`

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Last modified February 14 18:47 EST 2012. Contains 205663 sequences.