id:A108581 - OEIS Search Results

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Positive triangular numbers repeated their own number of times.

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1, 3, 3, 3, 6, 6, 6, 6, 6, 6, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`In terms of the repetition convolution operator #, where (sequence A) # (sequence B) = the sequence consisting of A(n) copies of B(n), then this sequence is the repetition self-convolution (A000217(n)-0) # (A000217(n)-0). Over the set of positive infinite integer sequences, # gives a nonassociative noncommutative groupoid with a left identity (A000012) but no right identity, where the left identity is also a right nullifier and idempotent.`
	FORMULA	`a(1) = 1, for n>1: a(A000217(n)-1) = a(A000217(n)) = ... = a(A000217(n+1)-2) = A000217(n).`
	CROSSREFS	`Cf. A000217, A002024, A072649, A074279.` `Sequence in context: A112669 A098529 A133774 this_sequence A073080 A057944 A080607` `Adjacent sequences: A108578 A108579 A108580 this_sequence A108582 A108583 A108584`
	KEYWORD	`easy,nonn`
	AUTHOR	`Jonathan Vos Post (jvospost3(AT)gmail.com), Jul 25 2005`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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