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Search: id:A000218
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| A000218 |
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Take sum of squares of digits of previous term. |
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+0
12
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| 3, 9, 81, 65, 61, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37
(list; graph; listen)
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OFFSET
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1,1
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REFERENCES
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R. Honsberger, Ingenuity in Math., Random House, 1970, p. 83.
A. Porges, A set of eight numbers, Amer. Math. Monthly, 52 (1945), 379-382.
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FORMULA
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Periodic with period 8.
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PROGRAM
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(PARI) A000218(n)=[3, 9, 81, 65, 61, 37, 58, 89, 145, 42, 20, 4, 16][n%8+(n%8<6 & n>7)*8] \\\\ [From M. F. Hasler (MHasler(AT)univ-ag.fr), May 24 2009]
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CROSSREFS
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Cf. A003132 (the iterated map), A003621, A039943, A099645, A031176, A007770, A000216 (starting with 2), A080709 (starting with 4), A000221 (starting with 5), A008460 (starting with 6), A008462 (starting with 8), A008463 (starting with 9), A139566 (starting with 15), A122065 (starting with 74169). [From M. F. Hasler (MHasler(AT)univ-ag.fr), May 24 2009]
Adjacent sequences: A000215 A000216 A000217 this_sequence A000219 A000220 A000221
Sequence in context: A132294 A032330 A018604 this_sequence A139731 A124049 A067623
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KEYWORD
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nonn,base
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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