id:A057944 - OEIS Search Results

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Largest triangular number less than or equal to n; write m-th triangular number m+1 times.

+0
6

0, 1, 1, 3, 3, 3, 6, 6, 6, 6, 10, 10, 10, 10, 10, 15, 15, 15, 15, 15, 15, 21, 21, 21, 21, 21, 21, 21, 28, 28, 28, 28, 28, 28, 28, 28, 36, 36, 36, 36, 36, 36, 36, 36, 36, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 66, 66, 66, 66, 66, 66 (list; graph; listen)

	OFFSET	`0,4`
	FORMULA	`a(n) =floor((sqrt(1+8n)-1)/2)floor((sqrt(1+8n)+1)/2)/2 =(trinv(n)(trinv(n)-1))/2 =A000217(A003056(n)) =n-A002262(n)`
	EXAMPLE	`a(35)=28 since 28 and 36 are successive triangular numbers and 28<=35<36`
	CROSSREFS	`Cf. A000217, A003056, A003056, A056944, A057945.` `Sequence in context: A133774 A108581 A073080 this_sequence A080607 A013322 A166273` `Adjacent sequences: A057941 A057942 A057943 this_sequence A057945 A057946 A057947`
	KEYWORD	`easy,nonn`
	AUTHOR	`Henry Bottomley (se16(AT)btinternet.com), Oct 05 2000`

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Last modified December 16 17:18 EST 2009. Contains 170825 sequences.

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