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Search: id:A000216
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| A000216 |
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Take sum of squares of digits of previous term. |
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+0
16
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| 2, 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, 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.
a(n)=(1/224)*{1027*(n mod 8)+3295*[(n+1) mod 8]-1157*[(n+2) mod 8]-457*[(n+3) mod 8]-177*[(n+4) mod 8]-177*[(n+5) mod 8]+75*[(n+6) mod 8]+859*[(n+7) mod 8]}-18*[C(2*n,n) mod 2], with n>=0 [From Paolo P. Lava (ppl(AT)spl.at), Oct 21 2008]
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PROGRAM
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(PARI) A000216(n)=[2, 4, 16, 37, 58, 89, 145, 42, 20][n%8+8*(n%8<2 & n>1)] \\\\ [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, A000218 (starting with 3), 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]
Sequence in context: A101926 A087965 A074411 this_sequence A110998 A051861 A048222
Adjacent sequences: A000213 A000214 A000215 this_sequence A000217 A000218 A000219
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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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