A117261 - OEIS

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A117261

Row sums of triangle A117260.

1, 2, 5, 21, 169, 2705, 86561, 5539905, 709107841, 181531607297, 92944182936065, 95174843326530561, 194918079132734588929, 798384452127680876253185, 6540365431829961738266091521, 107157347235102093119751643480065 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,2`
	FORMULA	`a(n) = Sum_{k=0..n} 2^(n(n-1)/2 - k(k-1)/2).`
	PROG	`(PARI) a(n)=sum(k=0, n, 2^((n-k)*(n+k-1)/2))`
	CROSSREFS	`Sequence in context: A144271 A193189 A176527 * A108021 A162437 A007570` `Adjacent sequences: A117258 A117259 A117260 * A117262 A117263 A117264`
	KEYWORD	`nonn`
	AUTHOR	`Paul D. Hanna (pauldhanna(AT)juno.com), Mar 14 2006`

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Last modified February 17 00:09 EST 2012. Contains 205978 sequences.