id:A144291 - OEIS Search Results

Search: id:A144291

Displaying 1-1 of 1 results found.

page 1

Triangular numbers n*(n-1)/2 with n and n -1 nonprime.

+0
5

0, 36, 45, 105, 120, 210, 231, 300, 325, 351, 378, 528, 561, 595, 630, 741, 780, 990, 1035, 1176, 1225, 1275, 1326, 1485, 1540, 1596, 1653, 1953, 2016, 2080, 2145, 2346, 2415, 2775, 2850, 2926, 3003, 3240, 3321, 3570, 3655, 3741, 3828, 4095, 4186, 4278 (list; graph; listen)

	OFFSET	`1,2`
	FORMULA	`a(n)=A000217(A068780(n-1)), n>1. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Dec 10 2008]`
	EXAMPLE	`If n=1, then 1(1-1)/2=0=a(1).` `If n=9, then 9(9-1)/2=36=a(2).` `etc.`
	CROSSREFS	`Cf. A000040, A141468.` `Sequence in context: A138566 A062034 A048034 this_sequence A068143 A167310 A083674` `Adjacent sequences: A144288 A144289 A144290 this_sequence A144292 A144293 A144294`
	KEYWORD	`nonn`
	AUTHOR	`Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Dec 01 2008`
	EXTENSIONS	`3570 inserted by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Dec 10 2008`

page 1

Search completed in 0.002 seconds

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

AT&T Labs Research