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Search: id:A114799
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| A114799 |
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Septuple factorial, 7-factorial, n!7, n!!!!!!!. |
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+0
4
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| 1, 1, 2, 3, 4, 5, 6, 7, 8, 18, 30, 44, 60, 78, 98, 120, 288, 510, 792, 1140, 1560, 2058, 2640, 6624, 12240, 19800, 29640, 42120, 57624, 76560, 198720, 379440, 633600, 978120, 1432080, 2016840, 2756160, 7352640, 14418720, 24710400, 39124800
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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It is well-known that a(36) + 1 = 2756161 is a multifactorial prime, as is a(35) + 1 = 2016841, a(31) + 1 = 379441, a(29) + 1 = 76561, a(26) + 1 = 29641, a(25) + 1 = 19801, a(24) + 1 = 12241, a(13) + 1 = 79, a(12) + 1 = 61, a(10) + 1 = 31, a(9) + 1 = 19, a(6) + 1 = 7, a(4) + 1 = 5. a(2) + 1 = 3.
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LINKS
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Eric Weisstein's World of Mathematics, Multifactorial.
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FORMULA
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a(n) = 1 for n<1, else a(n) = n*a(n-7).
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EXAMPLE
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a(40) = 40 * a(40-7) = 40 * a(33) = 40 * (33*a(26)) = 40 * 33 * (26*a(19)) = 40 * 33 * 26 * (19*a(12)) = 40 * 33 * 26 * 19 * (12*a(5)) = 40 * 33 * 26 * 19 * 12 5 = 39124800.
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CROSSREFS
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Sequence in context: A146029 A066759 A039050 this_sequence A055557 A103205 A039127
Adjacent sequences: A114796 A114797 A114798 this_sequence A114800 A114801 A114802
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Feb 18 2006
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