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Search: id:A000221
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| A000221 |
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Take sum of squares of digits of previous term. |
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+0
1
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| 5, 25, 29, 85, 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, 58, 89, 145
(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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MATHEMATICA
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NestList[Plus @@ IntegerDigits[ # ]^2 &, 5, 50]
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CROSSREFS
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Sequence in context: A070380 A068574 A000350 this_sequence A018612 A036127 A018639
Adjacent sequences: A000218 A000219 A000220 this_sequence A000222 A000223 A000224
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KEYWORD
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nonn,base,easy,nice
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AUTHOR
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njas
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