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A076506 3 people at a party are saying Hello to each other. Person 1 says Hello. Person 2 counts the times Hello has been said and says Hello twice that number. Person 3 says Hello 3 times the sum of Hello's and then it is Person 1 again. This is how the sum of Hello's. 1
1, 3, 12, 24, 72, 288, 576, 1728, 6912, 13824, 41472, 165888, 331776, 995328, 3981312, 7962624, 23887872, 95551488, 191102976, 573308928, 2293235712, 4586471424, 13759414272, 55037657088, 110075314176, 330225942528 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

PROG

(PARI) a(n)=if(n<1, 0, prod(k=1, n-1, k%3+2))

CROSSREFS

Cf. A076505.

Sequence in context: A050180 A028725 A047166 * A009776 A068967 A071355

Adjacent sequences:  A076503 A076504 A076505 * A076507 A076508 A076509

KEYWORD

nonn

AUTHOR

Jon Perry (perry(AT)globalnet.co.uk), Oct 15 2002

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Last modified February 16 02:51 EST 2012. Contains 205860 sequences.